diff --git a/core/events/events_abstract.js b/core/events/events_abstract.js
index d88d8efab..c20d894db 100644
--- a/core/events/events_abstract.js
+++ b/core/events/events_abstract.js
@@ -53,13 +53,13 @@ const Abstract = function() {
    * @type {boolean}
    */
   this.recordUndo = eventUtils.getRecordUndo();
-};
 
-/**
- * Whether or not the event is a UI event.
- * @type {boolean}
- */
-Abstract.prototype.isUiEvent = false;
+  /**
+   * Whether or not the event is a UI event.
+   * @type {boolean}
+   */
+  this.isUiEvent = false;
+};
 
 /**
  * Encode the event as JSON.
diff --git a/core/events/events_block_change.js b/core/events/events_block_change.js
index 4a9720ad8..cf8b6d0e9 100644
--- a/core/events/events_block_change.js
+++ b/core/events/events_block_change.js
@@ -17,7 +17,6 @@ goog.module('Blockly.Events.BlockChange');
 
 const Xml = goog.require('Blockly.Xml');
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {BlockBase} = goog.require('Blockly.Events.BlockBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -28,145 +27,149 @@ const {Block} = goog.requireType('Blockly.Block');
 
 /**
  * Class for a block change event.
- * @param {!Block=} opt_block The changed block.  Undefined for a blank
- *     event.
- * @param {string=} opt_element One of 'field', 'comment', 'disabled', etc.
- * @param {?string=} opt_name Name of input or field affected, or null.
- * @param {*=} opt_oldValue Previous value of element.
- * @param {*=} opt_newValue New value of element.
  * @extends {BlockBase}
- * @constructor
- * @alias Blockly.Events.BlockChange
  */
-const BlockChange = function(
-    opt_block, opt_element, opt_name, opt_oldValue, opt_newValue) {
-  BlockChange.superClass_.constructor.call(this, opt_block);
-  if (!opt_block) {
-    return;  // Blank event to be populated by fromJson.
-  }
-  this.element = typeof opt_element === 'undefined' ? '' : opt_element;
-  this.name = typeof opt_name === 'undefined' ? '' : opt_name;
-  this.oldValue = typeof opt_oldValue === 'undefined' ? '' : opt_oldValue;
-  this.newValue = typeof opt_newValue === 'undefined' ? '' : opt_newValue;
-};
-object.inherits(BlockChange, BlockBase);
+class BlockChange extends BlockBase {
+  /**
+   * @param {!Block=} opt_block The changed block.  Undefined for a blank
+   *     event.
+   * @param {string=} opt_element One of 'field', 'comment', 'disabled', etc.
+   * @param {?string=} opt_name Name of input or field affected, or null.
+   * @param {*=} opt_oldValue Previous value of element.
+   * @param {*=} opt_newValue New value of element.
+   * @alias Blockly.Events.BlockChange
+   */
+  constructor(opt_block, opt_element, opt_name, opt_oldValue, opt_newValue) {
+    super(opt_block);
 
-/**
- * Type of this event.
- * @type {string}
- */
-BlockChange.prototype.type = eventUtils.BLOCK_CHANGE;
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.BLOCK_CHANGE;
 
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-BlockChange.prototype.toJson = function() {
-  const json = BlockChange.superClass_.toJson.call(this);
-  json['element'] = this.element;
-  if (this.name) {
-    json['name'] = this.name;
-  }
-  json['oldValue'] = this.oldValue;
-  json['newValue'] = this.newValue;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-BlockChange.prototype.fromJson = function(json) {
-  BlockChange.superClass_.fromJson.call(this, json);
-  this.element = json['element'];
-  this.name = json['name'];
-  this.oldValue = json['oldValue'];
-  this.newValue = json['newValue'];
-};
-
-/**
- * Does this event record any change of state?
- * @return {boolean} False if something changed.
- */
-BlockChange.prototype.isNull = function() {
-  return this.oldValue === this.newValue;
-};
-
-/**
- * Run a change event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-BlockChange.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  const block = workspace.getBlockById(this.blockId);
-  if (!block) {
-    console.warn('Can\'t change non-existent block: ' + this.blockId);
-    return;
-  }
-  if (block.mutator) {
-    // Close the mutator (if open) since we don't want to update it.
-    block.mutator.setVisible(false);
-  }
-  const value = forward ? this.newValue : this.oldValue;
-  switch (this.element) {
-    case 'field': {
-      const field = block.getField(this.name);
-      if (field) {
-        field.setValue(value);
-      } else {
-        console.warn('Can\'t set non-existent field: ' + this.name);
-      }
-      break;
+    if (!opt_block) {
+      return;  // Blank event to be populated by fromJson.
     }
-    case 'comment':
-      block.setCommentText(/** @type {string} */ (value) || null);
-      break;
-    case 'collapsed':
-      block.setCollapsed(!!value);
-      break;
-    case 'disabled':
-      block.setEnabled(!value);
-      break;
-    case 'inline':
-      block.setInputsInline(!!value);
-      break;
-    case 'mutation': {
-      const oldState = BlockChange.getExtraBlockState_(
-          /** @type {!BlockSvg} */ (block));
-      if (block.loadExtraState) {
-        block.loadExtraState(JSON.parse(/** @type {string} */ (value) || '{}'));
-      } else if (block.domToMutation) {
-        block.domToMutation(
-            Xml.textToDom(/** @type {string} */ (value) || '<mutation/>'));
-      }
-      eventUtils.fire(
-          new BlockChange(block, 'mutation', null, oldState, value));
-      break;
-    }
-    default:
-      console.warn('Unknown change type: ' + this.element);
+    this.element = typeof opt_element === 'undefined' ? '' : opt_element;
+    this.name = typeof opt_name === 'undefined' ? '' : opt_name;
+    this.oldValue = typeof opt_oldValue === 'undefined' ? '' : opt_oldValue;
+    this.newValue = typeof opt_newValue === 'undefined' ? '' : opt_newValue;
   }
-};
 
-// TODO (#5397): Encapsulate this in the BlocklyMutationChange event when
-//    refactoring change events.
-/**
- * Returns the extra state of the given block (either as XML or a JSO, depending
- * on the block's definition).
- * @param {!BlockSvg} block The block to get the extra state of.
- * @return {string} A stringified version of the extra state of the given block.
- * @package
- */
-BlockChange.getExtraBlockState_ = function(block) {
-  if (block.saveExtraState) {
-    const state = block.saveExtraState();
-    return state ? JSON.stringify(state) : '';
-  } else if (block.mutationToDom) {
-    const state = block.mutationToDom();
-    return state ? Xml.domToText(state) : '';
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['element'] = this.element;
+    if (this.name) {
+      json['name'] = this.name;
+    }
+    json['oldValue'] = this.oldValue;
+    json['newValue'] = this.newValue;
+    return json;
   }
-  return '';
-};
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.element = json['element'];
+    this.name = json['name'];
+    this.oldValue = json['oldValue'];
+    this.newValue = json['newValue'];
+  }
+
+  /**
+   * Does this event record any change of state?
+   * @return {boolean} False if something changed.
+   */
+  isNull() {
+    return this.oldValue === this.newValue;
+  }
+
+  /**
+   * Run a change event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    const block = workspace.getBlockById(this.blockId);
+    if (!block) {
+      console.warn('Can\'t change non-existent block: ' + this.blockId);
+      return;
+    }
+    if (block.mutator) {
+      // Close the mutator (if open) since we don't want to update it.
+      block.mutator.setVisible(false);
+    }
+    const value = forward ? this.newValue : this.oldValue;
+    switch (this.element) {
+      case 'field': {
+        const field = block.getField(this.name);
+        if (field) {
+          field.setValue(value);
+        } else {
+          console.warn('Can\'t set non-existent field: ' + this.name);
+        }
+        break;
+      }
+      case 'comment':
+        block.setCommentText(/** @type {string} */ (value) || null);
+        break;
+      case 'collapsed':
+        block.setCollapsed(!!value);
+        break;
+      case 'disabled':
+        block.setEnabled(!value);
+        break;
+      case 'inline':
+        block.setInputsInline(!!value);
+        break;
+      case 'mutation': {
+        const oldState = BlockChange.getExtraBlockState_(
+            /** @type {!BlockSvg} */ (block));
+        if (block.loadExtraState) {
+          block.loadExtraState(
+              JSON.parse(/** @type {string} */ (value) || '{}'));
+        } else if (block.domToMutation) {
+          block.domToMutation(
+              Xml.textToDom(/** @type {string} */ (value) || '<mutation/>'));
+        }
+        eventUtils.fire(
+            new BlockChange(block, 'mutation', null, oldState, value));
+        break;
+      }
+      default:
+        console.warn('Unknown change type: ' + this.element);
+    }
+  }
+
+  // TODO (#5397): Encapsulate this in the BlocklyMutationChange event when
+  //    refactoring change events.
+  /**
+   * Returns the extra state of the given block (either as XML or a JSO,
+   * depending on the block's definition).
+   * @param {!BlockSvg} block The block to get the extra state of.
+   * @return {string} A stringified version of the extra state of the given
+   *     block.
+   * @package
+   */
+  static getExtraBlockState_(block) {
+    if (block.saveExtraState) {
+      const state = block.saveExtraState();
+      return state ? JSON.stringify(state) : '';
+    } else if (block.mutationToDom) {
+      const state = block.mutationToDom();
+      return state ? Xml.domToText(state) : '';
+    }
+    return '';
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.CHANGE, BlockChange);
 
diff --git a/core/events/events_block_create.js b/core/events/events_block_create.js
index 9a3254358..19ae8128d 100644
--- a/core/events/events_block_create.js
+++ b/core/events/events_block_create.js
@@ -18,7 +18,6 @@ goog.module('Blockly.Events.BlockCreate');
 const Xml = goog.require('Blockly.Xml');
 const blocks = goog.require('Blockly.serialization.blocks');
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {BlockBase} = goog.require('Blockly.Events.BlockBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -27,90 +26,93 @@ const {Block} = goog.requireType('Blockly.Block');
 
 /**
  * Class for a block creation event.
- * @param {!Block=} opt_block The created block.  Undefined for a blank
- *     event.
  * @extends {BlockBase}
- * @constructor
- * @alias Blockly.Events.BlockCreate
  */
-const BlockCreate = function(opt_block) {
-  BlockCreate.superClass_.constructor.call(this, opt_block);
-  if (!opt_block) {
-    return;  // Blank event to be populated by fromJson.
-  }
-  if (opt_block.isShadow()) {
-    // Moving shadow blocks is handled via disconnection.
-    this.recordUndo = false;
-  }
+class BlockCreate extends BlockBase {
+  /**
+   * @param {!Block=} opt_block The created block.  Undefined for a blank
+   *     event.
+   * @alias Blockly.Events.BlockCreate
+   */
+  constructor(opt_block) {
+    super(opt_block);
 
-  this.xml = Xml.blockToDomWithXY(opt_block);
-  this.ids = eventUtils.getDescendantIds(opt_block);
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.BLOCK_CREATE;
+
+    if (!opt_block) {
+      return;  // Blank event to be populated by fromJson.
+    }
+    if (opt_block.isShadow()) {
+      // Moving shadow blocks is handled via disconnection.
+      this.recordUndo = false;
+    }
+
+    this.xml = Xml.blockToDomWithXY(opt_block);
+    this.ids = eventUtils.getDescendantIds(opt_block);
+
+    /**
+     * JSON representation of the block that was just created.
+     * @type {!blocks.State}
+     */
+    this.json = /** @type {!blocks.State} */ (
+        blocks.save(opt_block, {addCoordinates: true}));
+  }
 
   /**
-   * JSON representation of the block that was just created.
-   * @type {!blocks.State}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.json = /** @type {!blocks.State} */ (
-      blocks.save(opt_block, {addCoordinates: true}));
-};
-object.inherits(BlockCreate, BlockBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-BlockCreate.prototype.type = eventUtils.BLOCK_CREATE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-BlockCreate.prototype.toJson = function() {
-  const json = BlockCreate.superClass_.toJson.call(this);
-  json['xml'] = Xml.domToText(this.xml);
-  json['ids'] = this.ids;
-  json['json'] = this.json;
-  if (!this.recordUndo) {
-    json['recordUndo'] = this.recordUndo;
+  toJson() {
+    const json = super.toJson();
+    json['xml'] = Xml.domToText(this.xml);
+    json['ids'] = this.ids;
+    json['json'] = this.json;
+    if (!this.recordUndo) {
+      json['recordUndo'] = this.recordUndo;
+    }
+    return json;
   }
-  return json;
-};
 
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-BlockCreate.prototype.fromJson = function(json) {
-  BlockCreate.superClass_.fromJson.call(this, json);
-  this.xml = Xml.textToDom(json['xml']);
-  this.ids = json['ids'];
-  this.json = /** @type {!blocks.State} */ (json['json']);
-  if (json['recordUndo'] !== undefined) {
-    this.recordUndo = json['recordUndo'];
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.xml = Xml.textToDom(json['xml']);
+    this.ids = json['ids'];
+    this.json = /** @type {!blocks.State} */ (json['json']);
+    if (json['recordUndo'] !== undefined) {
+      this.recordUndo = json['recordUndo'];
+    }
   }
-};
 
-/**
- * Run a creation event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-BlockCreate.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  if (forward) {
-    blocks.append(this.json, workspace);
-  } else {
-    for (let i = 0; i < this.ids.length; i++) {
-      const id = this.ids[i];
-      const block = workspace.getBlockById(id);
-      if (block) {
-        block.dispose(false);
-      } else if (id === this.blockId) {
-        // Only complain about root-level block.
-        console.warn('Can\'t uncreate non-existent block: ' + id);
+  /**
+   * Run a creation event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    if (forward) {
+      blocks.append(this.json, workspace);
+    } else {
+      for (let i = 0; i < this.ids.length; i++) {
+        const id = this.ids[i];
+        const block = workspace.getBlockById(id);
+        if (block) {
+          block.dispose(false);
+        } else if (id === this.blockId) {
+          // Only complain about root-level block.
+          console.warn('Can\'t uncreate non-existent block: ' + id);
+        }
       }
     }
   }
-};
+}
 
 registry.register(registry.Type.EVENT, eventUtils.CREATE, BlockCreate);
 
diff --git a/core/events/events_block_delete.js b/core/events/events_block_delete.js
index 80ef65d5e..633433980 100644
--- a/core/events/events_block_delete.js
+++ b/core/events/events_block_delete.js
@@ -18,7 +18,6 @@ goog.module('Blockly.Events.BlockDelete');
 const Xml = goog.require('Blockly.Xml');
 const blocks = goog.require('Blockly.serialization.blocks');
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {BlockBase} = goog.require('Blockly.Events.BlockBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -27,102 +26,105 @@ const {Block} = goog.requireType('Blockly.Block');
 
 /**
  * Class for a block deletion event.
- * @param {!Block=} opt_block The deleted block.  Undefined for a blank
- *     event.
  * @extends {BlockBase}
- * @constructor
- * @alias Blockly.Events.BlockDelete
  */
-const BlockDelete = function(opt_block) {
-  BlockDelete.superClass_.constructor.call(this, opt_block);
-  if (!opt_block) {
-    return;  // Blank event to be populated by fromJson.
-  }
-  if (opt_block.getParent()) {
-    throw Error('Connected blocks cannot be deleted.');
-  }
-  if (opt_block.isShadow()) {
-    // Respawning shadow blocks is handled via disconnection.
-    this.recordUndo = false;
-  }
-
-  this.oldXml = Xml.blockToDomWithXY(opt_block);
-  this.ids = eventUtils.getDescendantIds(opt_block);
-
+class BlockDelete extends BlockBase {
   /**
-   * Was the block that was just deleted a shadow?
-   * @type {boolean}
+   * @param {!Block=} opt_block The deleted block.  Undefined for a blank
+   *     event.
+   * @alias Blockly.Events.BlockDelete
    */
-  this.wasShadow = opt_block.isShadow();
+  constructor(opt_block) {
+    super(opt_block);
 
-  /**
-   * JSON representation of the block that was just deleted.
-   * @type {!blocks.State}
-   */
-  this.oldJson = /** @type {!blocks.State} */ (
-      blocks.save(opt_block, {addCoordinates: true}));
-};
-object.inherits(BlockDelete, BlockBase);
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.BLOCK_DELETE;
 
-/**
- * Type of this event.
- * @type {string}
- */
-BlockDelete.prototype.type = eventUtils.BLOCK_DELETE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-BlockDelete.prototype.toJson = function() {
-  const json = BlockDelete.superClass_.toJson.call(this);
-  json['oldXml'] = Xml.domToText(this.oldXml);
-  json['ids'] = this.ids;
-  json['wasShadow'] = this.wasShadow;
-  json['oldJson'] = this.oldJson;
-  if (!this.recordUndo) {
-    json['recordUndo'] = this.recordUndo;
-  }
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-BlockDelete.prototype.fromJson = function(json) {
-  BlockDelete.superClass_.fromJson.call(this, json);
-  this.oldXml = Xml.textToDom(json['oldXml']);
-  this.ids = json['ids'];
-  this.wasShadow =
-      json['wasShadow'] || this.oldXml.tagName.toLowerCase() === 'shadow';
-  this.oldJson = /** @type {!blocks.State} */ (json['oldJson']);
-  if (json['recordUndo'] !== undefined) {
-    this.recordUndo = json['recordUndo'];
-  }
-};
-
-/**
- * Run a deletion event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-BlockDelete.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  if (forward) {
-    for (let i = 0; i < this.ids.length; i++) {
-      const id = this.ids[i];
-      const block = workspace.getBlockById(id);
-      if (block) {
-        block.dispose(false);
-      } else if (id === this.blockId) {
-        // Only complain about root-level block.
-        console.warn('Can\'t delete non-existent block: ' + id);
-      }
+    if (!opt_block) {
+      return;  // Blank event to be populated by fromJson.
     }
-  } else {
-    blocks.append(this.oldJson, workspace);
+    if (opt_block.getParent()) {
+      throw Error('Connected blocks cannot be deleted.');
+    }
+    if (opt_block.isShadow()) {
+      // Respawning shadow blocks is handled via disconnection.
+      this.recordUndo = false;
+    }
+
+    this.oldXml = Xml.blockToDomWithXY(opt_block);
+    this.ids = eventUtils.getDescendantIds(opt_block);
+
+    /**
+     * Was the block that was just deleted a shadow?
+     * @type {boolean}
+     */
+    this.wasShadow = opt_block.isShadow();
+
+    /**
+     * JSON representation of the block that was just deleted.
+     * @type {!blocks.State}
+     */
+    this.oldJson = /** @type {!blocks.State} */ (
+        blocks.save(opt_block, {addCoordinates: true}));
   }
-};
+
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['oldXml'] = Xml.domToText(this.oldXml);
+    json['ids'] = this.ids;
+    json['wasShadow'] = this.wasShadow;
+    json['oldJson'] = this.oldJson;
+    if (!this.recordUndo) {
+      json['recordUndo'] = this.recordUndo;
+    }
+    return json;
+  }
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.oldXml = Xml.textToDom(json['oldXml']);
+    this.ids = json['ids'];
+    this.wasShadow =
+        json['wasShadow'] || this.oldXml.tagName.toLowerCase() === 'shadow';
+    this.oldJson = /** @type {!blocks.State} */ (json['oldJson']);
+    if (json['recordUndo'] !== undefined) {
+      this.recordUndo = json['recordUndo'];
+    }
+  }
+
+  /**
+   * Run a deletion event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    if (forward) {
+      for (let i = 0; i < this.ids.length; i++) {
+        const id = this.ids[i];
+        const block = workspace.getBlockById(id);
+        if (block) {
+          block.dispose(false);
+        } else if (id === this.blockId) {
+          // Only complain about root-level block.
+          console.warn('Can\'t delete non-existent block: ' + id);
+        }
+      }
+    } else {
+      blocks.append(this.oldJson, workspace);
+    }
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.DELETE, BlockDelete);
 
diff --git a/core/events/events_block_drag.js b/core/events/events_block_drag.js
index 432246eb8..42fb45bee 100644
--- a/core/events/events_block_drag.js
+++ b/core/events/events_block_drag.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.BlockDrag');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 /* eslint-disable-next-line no-unused-vars */
 const {Block} = goog.requireType('Blockly.Block');
@@ -25,63 +24,65 @@ const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 /**
  * Class for a block drag event.
- * @param {!Block=} opt_block The top block in the stack that is being
- *    dragged. Undefined for a blank event.
- * @param {boolean=} opt_isStart Whether this is the start of a block drag.
- *    Undefined for a blank event.
- * @param {!Array<!Block>=} opt_blocks The blocks affected by this
- *    drag. Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.BlockDrag
  */
-const BlockDrag = function(opt_block, opt_isStart, opt_blocks) {
-  const workspaceId = opt_block ? opt_block.workspace.id : undefined;
-  BlockDrag.superClass_.constructor.call(this, workspaceId);
-  this.blockId = opt_block ? opt_block.id : null;
+class BlockDrag extends UiBase {
+  /**
+   * @param {!Block=} opt_block The top block in the stack that is being
+   *    dragged. Undefined for a blank event.
+   * @param {boolean=} opt_isStart Whether this is the start of a block drag.
+   *    Undefined for a blank event.
+   * @param {!Array<!Block>=} opt_blocks The blocks affected by this
+   *    drag. Undefined for a blank event.
+   * @alias Blockly.Events.BlockDrag
+   */
+  constructor(opt_block, opt_isStart, opt_blocks) {
+    const workspaceId = opt_block ? opt_block.workspace.id : undefined;
+    super(workspaceId);
+    this.blockId = opt_block ? opt_block.id : null;
+
+    /**
+     * Whether this is the start of a block drag.
+     * @type {boolean|undefined}
+     */
+    this.isStart = opt_isStart;
+
+    /**
+     * The blocks affected by this drag event.
+     * @type {!Array<!Block>|undefined}
+     */
+    this.blocks = opt_blocks;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.BLOCK_DRAG;
+  }
 
   /**
-   * Whether this is the start of a block drag.
-   * @type {boolean|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.isStart = opt_isStart;
+  toJson() {
+    const json = super.toJson();
+    json['isStart'] = this.isStart;
+    json['blockId'] = this.blockId;
+    json['blocks'] = this.blocks;
+    return json;
+  }
 
   /**
-   * The blocks affected by this drag event.
-   * @type {!Array<!Block>|undefined}
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
    */
-  this.blocks = opt_blocks;
-};
-object.inherits(BlockDrag, UiBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-BlockDrag.prototype.type = eventUtils.BLOCK_DRAG;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-BlockDrag.prototype.toJson = function() {
-  const json = BlockDrag.superClass_.toJson.call(this);
-  json['isStart'] = this.isStart;
-  json['blockId'] = this.blockId;
-  json['blocks'] = this.blocks;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-BlockDrag.prototype.fromJson = function(json) {
-  BlockDrag.superClass_.fromJson.call(this, json);
-  this.isStart = json['isStart'];
-  this.blockId = json['blockId'];
-  this.blocks = json['blocks'];
-};
+  fromJson(json) {
+    super.fromJson(json);
+    this.isStart = json['isStart'];
+    this.blockId = json['blockId'];
+    this.blocks = json['blocks'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.BLOCK_DRAG, BlockDrag);
 
diff --git a/core/events/events_block_move.js b/core/events/events_block_move.js
index a90d74bd2..c0a7adb95 100644
--- a/core/events/events_block_move.js
+++ b/core/events/events_block_move.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.BlockMove');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {BlockBase} = goog.require('Blockly.Events.BlockBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -27,168 +26,176 @@ const {Coordinate} = goog.require('Blockly.utils.Coordinate');
 
 /**
  * Class for a block move event.  Created before the move.
- * @param {!Block=} opt_block The moved block.  Undefined for a blank
- *     event.
  * @extends {BlockBase}
- * @constructor
- * @alias Blockly.Events.BlockMove
  */
-const BlockMove = function(opt_block) {
-  BlockMove.superClass_.constructor.call(this, opt_block);
-  if (!opt_block) {
-    return;  // Blank event to be populated by fromJson.
-  }
-  if (opt_block.isShadow()) {
-    // Moving shadow blocks is handled via disconnection.
-    this.recordUndo = false;
-  }
+class BlockMove extends BlockBase {
+  /**
+   * @param {!Block=} opt_block The moved block.  Undefined for a blank
+   *     event.
+   * @alias Blockly.Events.BlockMove
+   */
+  constructor(opt_block) {
+    super(opt_block);
 
-  const location = this.currentLocation_();
-  this.oldParentId = location.parentId;
-  this.oldInputName = location.inputName;
-  this.oldCoordinate = location.coordinate;
-};
-object.inherits(BlockMove, BlockBase);
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.BLOCK_MOVE;
 
-/**
- * Type of this event.
- * @type {string}
- */
-BlockMove.prototype.type = eventUtils.BLOCK_MOVE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-BlockMove.prototype.toJson = function() {
-  const json = BlockMove.superClass_.toJson.call(this);
-  if (this.newParentId) {
-    json['newParentId'] = this.newParentId;
-  }
-  if (this.newInputName) {
-    json['newInputName'] = this.newInputName;
-  }
-  if (this.newCoordinate) {
-    json['newCoordinate'] = Math.round(this.newCoordinate.x) + ',' +
-        Math.round(this.newCoordinate.y);
-  }
-  if (!this.recordUndo) {
-    json['recordUndo'] = this.recordUndo;
-  }
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-BlockMove.prototype.fromJson = function(json) {
-  BlockMove.superClass_.fromJson.call(this, json);
-  this.newParentId = json['newParentId'];
-  this.newInputName = json['newInputName'];
-  if (json['newCoordinate']) {
-    const xy = json['newCoordinate'].split(',');
-    this.newCoordinate = new Coordinate(Number(xy[0]), Number(xy[1]));
-  }
-  if (json['recordUndo'] !== undefined) {
-    this.recordUndo = json['recordUndo'];
-  }
-};
-
-/**
- * Record the block's new location.  Called after the move.
- */
-BlockMove.prototype.recordNew = function() {
-  const location = this.currentLocation_();
-  this.newParentId = location.parentId;
-  this.newInputName = location.inputName;
-  this.newCoordinate = location.coordinate;
-};
-
-/**
- * Returns the parentId and input if the block is connected,
- *   or the XY location if disconnected.
- * @return {!Object} Collection of location info.
- * @private
- */
-BlockMove.prototype.currentLocation_ = function() {
-  const workspace = this.getEventWorkspace_();
-  const block = workspace.getBlockById(this.blockId);
-  const location = {};
-  const parent = block.getParent();
-  if (parent) {
-    location.parentId = parent.id;
-    const input = parent.getInputWithBlock(block);
-    if (input) {
-      location.inputName = input.name;
+    if (!opt_block) {
+      return;  // Blank event to be populated by fromJson.
+    }
+    if (opt_block.isShadow()) {
+      // Moving shadow blocks is handled via disconnection.
+      this.recordUndo = false;
     }
-  } else {
-    location.coordinate = block.getRelativeToSurfaceXY();
-  }
-  return location;
-};
 
-/**
- * Does this event record any change of state?
- * @return {boolean} False if something changed.
- */
-BlockMove.prototype.isNull = function() {
-  return this.oldParentId === this.newParentId &&
-      this.oldInputName === this.newInputName &&
-      Coordinate.equals(this.oldCoordinate, this.newCoordinate);
-};
+    const location = this.currentLocation_();
+    this.oldParentId = location.parentId;
+    this.oldInputName = location.inputName;
+    this.oldCoordinate = location.coordinate;
 
-/**
- * Run a move event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-BlockMove.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  const block = workspace.getBlockById(this.blockId);
-  if (!block) {
-    console.warn('Can\'t move non-existent block: ' + this.blockId);
-    return;
+    this.newParentId = null;
+    this.newInputName = null;
+    this.newCoordinate = null;
   }
-  const parentId = forward ? this.newParentId : this.oldParentId;
-  const inputName = forward ? this.newInputName : this.oldInputName;
-  const coordinate = forward ? this.newCoordinate : this.oldCoordinate;
-  let parentBlock;
-  if (parentId) {
-    parentBlock = workspace.getBlockById(parentId);
-    if (!parentBlock) {
-      console.warn('Can\'t connect to non-existent block: ' + parentId);
+
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    if (this.newParentId) {
+      json['newParentId'] = this.newParentId;
+    }
+    if (this.newInputName) {
+      json['newInputName'] = this.newInputName;
+    }
+    if (this.newCoordinate) {
+      json['newCoordinate'] = Math.round(this.newCoordinate.x) + ',' +
+          Math.round(this.newCoordinate.y);
+    }
+    if (!this.recordUndo) {
+      json['recordUndo'] = this.recordUndo;
+    }
+    return json;
+  }
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.newParentId = json['newParentId'];
+    this.newInputName = json['newInputName'];
+    if (json['newCoordinate']) {
+      const xy = json['newCoordinate'].split(',');
+      this.newCoordinate = new Coordinate(Number(xy[0]), Number(xy[1]));
+    }
+    if (json['recordUndo'] !== undefined) {
+      this.recordUndo = json['recordUndo'];
+    }
+  }
+
+  /**
+   * Record the block's new location.  Called after the move.
+   */
+  recordNew() {
+    const location = this.currentLocation_();
+    this.newParentId = location.parentId;
+    this.newInputName = location.inputName;
+    this.newCoordinate = location.coordinate;
+  }
+
+  /**
+   * Returns the parentId and input if the block is connected,
+   *   or the XY location if disconnected.
+   * @return {!Object} Collection of location info.
+   * @private
+   */
+  currentLocation_() {
+    const workspace = this.getEventWorkspace_();
+    const block = workspace.getBlockById(this.blockId);
+    const location = {};
+    const parent = block.getParent();
+    if (parent) {
+      location.parentId = parent.id;
+      const input = parent.getInputWithBlock(block);
+      if (input) {
+        location.inputName = input.name;
+      }
+    } else {
+      location.coordinate = block.getRelativeToSurfaceXY();
+    }
+    return location;
+  }
+
+  /**
+   * Does this event record any change of state?
+   * @return {boolean} False if something changed.
+   */
+  isNull() {
+    return this.oldParentId === this.newParentId &&
+        this.oldInputName === this.newInputName &&
+        Coordinate.equals(this.oldCoordinate, this.newCoordinate);
+  }
+
+  /**
+   * Run a move event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    const block = workspace.getBlockById(this.blockId);
+    if (!block) {
+      console.warn('Can\'t move non-existent block: ' + this.blockId);
       return;
     }
-  }
-  if (block.getParent()) {
-    block.unplug();
-  }
-  if (coordinate) {
-    const xy = block.getRelativeToSurfaceXY();
-    block.moveBy(coordinate.x - xy.x, coordinate.y - xy.y);
-  } else {
-    let blockConnection = block.outputConnection;
-    if (!blockConnection ||
-        (block.previousConnection && block.previousConnection.isConnected())) {
-      blockConnection = block.previousConnection;
-    }
-    let parentConnection;
-    const connectionType = blockConnection.type;
-    if (inputName) {
-      const input = parentBlock.getInput(inputName);
-      if (input) {
-        parentConnection = input.connection;
+    const parentId = forward ? this.newParentId : this.oldParentId;
+    const inputName = forward ? this.newInputName : this.oldInputName;
+    const coordinate = forward ? this.newCoordinate : this.oldCoordinate;
+    let parentBlock;
+    if (parentId) {
+      parentBlock = workspace.getBlockById(parentId);
+      if (!parentBlock) {
+        console.warn('Can\'t connect to non-existent block: ' + parentId);
+        return;
       }
-    } else if (connectionType === ConnectionType.PREVIOUS_STATEMENT) {
-      parentConnection = parentBlock.nextConnection;
     }
-    if (parentConnection) {
-      blockConnection.connect(parentConnection);
+    if (block.getParent()) {
+      block.unplug();
+    }
+    if (coordinate) {
+      const xy = block.getRelativeToSurfaceXY();
+      block.moveBy(coordinate.x - xy.x, coordinate.y - xy.y);
     } else {
-      console.warn('Can\'t connect to non-existent input: ' + inputName);
+      let blockConnection = block.outputConnection;
+      if (!blockConnection ||
+          (block.previousConnection &&
+           block.previousConnection.isConnected())) {
+        blockConnection = block.previousConnection;
+      }
+      let parentConnection;
+      const connectionType = blockConnection.type;
+      if (inputName) {
+        const input = parentBlock.getInput(inputName);
+        if (input) {
+          parentConnection = input.connection;
+        }
+      } else if (connectionType === ConnectionType.PREVIOUS_STATEMENT) {
+        parentConnection = parentBlock.nextConnection;
+      }
+      if (parentConnection) {
+        blockConnection.connect(parentConnection);
+      } else {
+        console.warn('Can\'t connect to non-existent input: ' + inputName);
+      }
     }
   }
-};
+}
 
 registry.register(registry.Type.EVENT, eventUtils.MOVE, BlockMove);
 
diff --git a/core/events/events_bubble_open.js b/core/events/events_bubble_open.js
index 9c76fd751..95099951c 100644
--- a/core/events/events_bubble_open.js
+++ b/core/events/events_bubble_open.js
@@ -52,15 +52,15 @@ const BubbleOpen = function(opt_block, opt_isOpen, opt_bubbleType) {
    * @type {string|undefined}
    */
   this.bubbleType = opt_bubbleType;
+
+  /**
+   * Type of this event.
+   * @type {string}
+   */
+  this.type = eventUtils.BUBBLE_OPEN;
 };
 object.inherits(BubbleOpen, UiBase);
 
-/**
- * Type of this event.
- * @type {string}
- */
-BubbleOpen.prototype.type = eventUtils.BUBBLE_OPEN;
-
 /**
  * Encode the event as JSON.
  * @return {!Object} JSON representation.
diff --git a/core/events/events_click.js b/core/events/events_click.js
index 0bc9aa972..a855ea63c 100644
--- a/core/events/events_click.js
+++ b/core/events/events_click.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.Click');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 /* eslint-disable-next-line no-unused-vars */
 const {Block} = goog.requireType('Blockly.Block');
@@ -25,58 +24,63 @@ const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 /**
  * Class for a click event.
- * @param {?Block=} opt_block The affected block. Null for click events
- *    that do not have an associated block (i.e. workspace click). Undefined
- *    for a blank event.
- * @param {?string=} opt_workspaceId The workspace identifier for this event.
- *    Not used if block is passed. Undefined for a blank event.
- * @param {string=} opt_targetType The type of element targeted by this click
- *    event. Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.Click
  */
-const Click = function(opt_block, opt_workspaceId, opt_targetType) {
-  const workspaceId = opt_block ? opt_block.workspace.id : opt_workspaceId;
-  Click.superClass_.constructor.call(this, workspaceId);
-  this.blockId = opt_block ? opt_block.id : null;
+class Click extends UiBase {
+  /**
+   * @param {?Block=} opt_block The affected block. Null for click events
+   *    that do not have an associated block (i.e. workspace click). Undefined
+   *    for a blank event.
+   * @param {?string=} opt_workspaceId The workspace identifier for this event.
+   *    Not used if block is passed. Undefined for a blank event.
+   * @param {string=} opt_targetType The type of element targeted by this click
+   *    event. Undefined for a blank event.
+   * @alias Blockly.Events.Click
+   */
+  constructor(opt_block, opt_workspaceId, opt_targetType) {
+    let workspaceId = opt_block ? opt_block.workspace.id : opt_workspaceId;
+    if (workspaceId === null) {
+      workspaceId = undefined;
+    }
+    super(workspaceId);
+    this.blockId = opt_block ? opt_block.id : null;
+
+    /**
+     * The type of element targeted by this click event.
+     * @type {string|undefined}
+     */
+    this.targetType = opt_targetType;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.CLICK;
+  }
 
   /**
-   * The type of element targeted by this click event.
-   * @type {string|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.targetType = opt_targetType;
-};
-object.inherits(Click, UiBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-Click.prototype.type = eventUtils.CLICK;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-Click.prototype.toJson = function() {
-  const json = Click.superClass_.toJson.call(this);
-  json['targetType'] = this.targetType;
-  if (this.blockId) {
-    json['blockId'] = this.blockId;
+  toJson() {
+    const json = super.toJson();
+    json['targetType'] = this.targetType;
+    if (this.blockId) {
+      json['blockId'] = this.blockId;
+    }
+    return json;
   }
-  return json;
-};
 
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-Click.prototype.fromJson = function(json) {
-  Click.superClass_.fromJson.call(this, json);
-  this.targetType = json['targetType'];
-  this.blockId = json['blockId'];
-};
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.targetType = json['targetType'];
+    this.blockId = json['blockId'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.CLICK, Click);
 
diff --git a/core/events/events_comment_change.js b/core/events/events_comment_change.js
index 1f6b44ba3..ec6b54e05 100644
--- a/core/events/events_comment_change.js
+++ b/core/events/events_comment_change.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.CommentChange');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {CommentBase} = goog.require('Blockly.Events.CommentBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -25,77 +24,80 @@ const {WorkspaceComment} = goog.requireType('Blockly.WorkspaceComment');
 
 /**
  * Class for a comment change event.
- * @param {!WorkspaceComment=} opt_comment The comment that is being
- *     changed.  Undefined for a blank event.
- * @param {string=} opt_oldContents Previous contents of the comment.
- * @param {string=} opt_newContents New contents of the comment.
  * @extends {CommentBase}
- * @constructor
- * @alias Blockly.Events.CommentChange
  */
-const CommentChange = function(opt_comment, opt_oldContents, opt_newContents) {
-  CommentChange.superClass_.constructor.call(this, opt_comment);
-  if (!opt_comment) {
-    return;  // Blank event to be populated by fromJson.
+class CommentChange extends CommentBase {
+  /**
+   * @param {!WorkspaceComment=} opt_comment The comment that is being
+   *     changed.  Undefined for a blank event.
+   * @param {string=} opt_oldContents Previous contents of the comment.
+   * @param {string=} opt_newContents New contents of the comment.
+   * @alias Blockly.Events.CommentChange
+   */
+  constructor(opt_comment, opt_oldContents, opt_newContents) {
+    super(opt_comment);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.COMMENT_CHANGE;
+
+    if (!opt_comment) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    this.oldContents_ =
+        typeof opt_oldContents === 'undefined' ? '' : opt_oldContents;
+    this.newContents_ =
+        typeof opt_newContents === 'undefined' ? '' : opt_newContents;
   }
 
-  this.oldContents_ =
-      typeof opt_oldContents === 'undefined' ? '' : opt_oldContents;
-  this.newContents_ =
-      typeof opt_newContents === 'undefined' ? '' : opt_newContents;
-};
-object.inherits(CommentChange, CommentBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-CommentChange.prototype.type = eventUtils.COMMENT_CHANGE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-CommentChange.prototype.toJson = function() {
-  const json = CommentChange.superClass_.toJson.call(this);
-  json['oldContents'] = this.oldContents_;
-  json['newContents'] = this.newContents_;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-CommentChange.prototype.fromJson = function(json) {
-  CommentChange.superClass_.fromJson.call(this, json);
-  this.oldContents_ = json['oldContents'];
-  this.newContents_ = json['newContents'];
-};
-
-/**
- * Does this event record any change of state?
- * @return {boolean} False if something changed.
- */
-CommentChange.prototype.isNull = function() {
-  return this.oldContents_ === this.newContents_;
-};
-
-/**
- * Run a change event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-CommentChange.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  const comment = workspace.getCommentById(this.commentId);
-  if (!comment) {
-    console.warn('Can\'t change non-existent comment: ' + this.commentId);
-    return;
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['oldContents'] = this.oldContents_;
+    json['newContents'] = this.newContents_;
+    return json;
   }
-  const contents = forward ? this.newContents_ : this.oldContents_;
 
-  comment.setContent(contents);
-};
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.oldContents_ = json['oldContents'];
+    this.newContents_ = json['newContents'];
+  }
+
+  /**
+   * Does this event record any change of state?
+   * @return {boolean} False if something changed.
+   */
+  isNull() {
+    return this.oldContents_ === this.newContents_;
+  }
+
+  /**
+   * Run a change event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    const comment = workspace.getCommentById(this.commentId);
+    if (!comment) {
+      console.warn('Can\'t change non-existent comment: ' + this.commentId);
+      return;
+    }
+    const contents = forward ? this.newContents_ : this.oldContents_;
+
+    comment.setContent(contents);
+  }
+}
 
 registry.register(
     registry.Type.EVENT, eventUtils.COMMENT_CHANGE, CommentChange);
diff --git a/core/events/events_comment_create.js b/core/events/events_comment_create.js
index 5d9cb8d79..f3d15659b 100644
--- a/core/events/events_comment_create.js
+++ b/core/events/events_comment_create.js
@@ -17,7 +17,6 @@ goog.module('Blockly.Events.CommentCreate');
 
 const Xml = goog.require('Blockly.Xml');
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {CommentBase} = goog.require('Blockly.Events.CommentBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -26,55 +25,58 @@ const {WorkspaceComment} = goog.requireType('Blockly.WorkspaceComment');
 
 /**
  * Class for a comment creation event.
- * @param {!WorkspaceComment=} opt_comment The created comment.
- *     Undefined for a blank event.
  * @extends {CommentBase}
- * @constructor
- * @alias Blockly.Events.CommentCreate
  */
-const CommentCreate = function(opt_comment) {
-  CommentCreate.superClass_.constructor.call(this, opt_comment);
-  if (!opt_comment) {
-    return;  // Blank event to be populated by fromJson.
+class CommentCreate extends CommentBase {
+  /**
+   * @param {!WorkspaceComment=} opt_comment The created comment.
+   *     Undefined for a blank event.
+   * @alias Blockly.Events.CommentCreate
+   */
+  constructor(opt_comment) {
+    super(opt_comment);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.COMMENT_CREATE;
+
+    if (!opt_comment) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    this.xml = opt_comment.toXmlWithXY();
   }
 
-  this.xml = opt_comment.toXmlWithXY();
-};
-object.inherits(CommentCreate, CommentBase);
+  // TODO (#1266): "Full" and "minimal" serialization.
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['xml'] = Xml.domToText(this.xml);
+    return json;
+  }
 
-/**
- * Type of this event.
- * @type {string}
- */
-CommentCreate.prototype.type = eventUtils.COMMENT_CREATE;
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.xml = Xml.textToDom(json['xml']);
+  }
 
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-// TODO (#1266): "Full" and "minimal" serialization.
-CommentCreate.prototype.toJson = function() {
-  const json = CommentCreate.superClass_.toJson.call(this);
-  json['xml'] = Xml.domToText(this.xml);
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-CommentCreate.prototype.fromJson = function(json) {
-  CommentCreate.superClass_.fromJson.call(this, json);
-  this.xml = Xml.textToDom(json['xml']);
-};
-
-/**
- * Run a creation event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-CommentCreate.prototype.run = function(forward) {
-  CommentBase.CommentCreateDeleteHelper(this, forward);
-};
+  /**
+   * Run a creation event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    CommentBase.CommentCreateDeleteHelper(this, forward);
+  }
+}
 
 registry.register(
     registry.Type.EVENT, eventUtils.COMMENT_CREATE, CommentCreate);
diff --git a/core/events/events_comment_delete.js b/core/events/events_comment_delete.js
index 54e1df4ba..fc426ca5e 100644
--- a/core/events/events_comment_delete.js
+++ b/core/events/events_comment_delete.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.CommentDelete');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {CommentBase} = goog.require('Blockly.Events.CommentBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -25,53 +24,56 @@ const {WorkspaceComment} = goog.requireType('Blockly.WorkspaceComment');
 
 /**
  * Class for a comment deletion event.
- * @param {!WorkspaceComment=} opt_comment The deleted comment.
- *     Undefined for a blank event.
  * @extends {CommentBase}
- * @constructor
- * @alias Blockly.Events.CommentDelete
  */
-const CommentDelete = function(opt_comment) {
-  CommentDelete.superClass_.constructor.call(this, opt_comment);
-  if (!opt_comment) {
-    return;  // Blank event to be populated by fromJson.
+class CommentDelete extends CommentBase {
+  /**
+   * @param {!WorkspaceComment=} opt_comment The deleted comment.
+   *     Undefined for a blank event.
+   * @alias Blockly.Events.CommentDelete
+   */
+  constructor(opt_comment) {
+    super(opt_comment);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.COMMENT_DELETE;
+
+    if (!opt_comment) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    this.xml = opt_comment.toXmlWithXY();
   }
 
-  this.xml = opt_comment.toXmlWithXY();
-};
-object.inherits(CommentDelete, CommentBase);
+  // TODO (#1266): "Full" and "minimal" serialization.
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    return json;
+  }
 
-/**
- * Type of this event.
- * @type {string}
- */
-CommentDelete.prototype.type = eventUtils.COMMENT_DELETE;
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+  }
 
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-// TODO (#1266): "Full" and "minimal" serialization.
-CommentDelete.prototype.toJson = function() {
-  const json = CommentDelete.superClass_.toJson.call(this);
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-CommentDelete.prototype.fromJson = function(json) {
-  CommentDelete.superClass_.fromJson.call(this, json);
-};
-
-/**
- * Run a creation event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-CommentDelete.prototype.run = function(forward) {
-  CommentBase.CommentCreateDeleteHelper(this, !forward);
-};
+  /**
+   * Run a creation event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    CommentBase.CommentCreateDeleteHelper(this, !forward);
+  }
+}
 
 registry.register(
     registry.Type.EVENT, eventUtils.COMMENT_DELETE, CommentDelete);
diff --git a/core/events/events_comment_move.js b/core/events/events_comment_move.js
index 51ba01ab6..7545c619f 100644
--- a/core/events/events_comment_move.js
+++ b/core/events/events_comment_move.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.CommentMove');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {CommentBase} = goog.require('Blockly.Events.CommentBase');
 const {Coordinate} = goog.require('Blockly.utils.Coordinate');
@@ -26,129 +25,132 @@ const {WorkspaceComment} = goog.requireType('Blockly.WorkspaceComment');
 
 /**
  * Class for a comment move event.  Created before the move.
- * @param {!WorkspaceComment=} opt_comment The comment that is being
- *     moved.  Undefined for a blank event.
  * @extends {CommentBase}
- * @constructor
- * @alias Blockly.Events.CommentMove
  */
-const CommentMove = function(opt_comment) {
-  CommentMove.superClass_.constructor.call(this, opt_comment);
-  if (!opt_comment) {
-    return;  // Blank event to be populated by fromJson.
+class CommentMove extends CommentBase {
+  /**
+   * @param {!WorkspaceComment=} opt_comment The comment that is being
+   *     moved.  Undefined for a blank event.
+   * @alias Blockly.Events.CommentMove
+   */
+  constructor(opt_comment) {
+    super(opt_comment);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.COMMENT_MOVE;
+
+    if (!opt_comment) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    /**
+     * The comment that is being moved.  Will be cleared after recording the new
+     * location.
+     * @type {WorkspaceComment}
+     */
+    this.comment_ = opt_comment;
+
+    /**
+     * The location before the move, in workspace coordinates.
+     * @type {!Coordinate}
+     */
+    this.oldCoordinate_ = opt_comment.getXY();
+
+    /**
+     * The location after the move, in workspace coordinates.
+     * @type {Coordinate}
+     */
+    this.newCoordinate_ = null;
   }
 
   /**
-   * The comment that is being moved.  Will be cleared after recording the new
-   * location.
-   * @type {WorkspaceComment}
+   * Record the comment's new location.  Called after the move.  Can only be
+   * called once.
    */
-  this.comment_ = opt_comment;
+  recordNew() {
+    if (!this.comment_) {
+      throw Error(
+          'Tried to record the new position of a comment on the ' +
+          'same event twice.');
+    }
+    this.newCoordinate_ = this.comment_.getXY();
+    this.comment_ = null;
+  }
 
   /**
-   * The location before the move, in workspace coordinates.
-   * @type {!Coordinate}
+   * Override the location before the move.  Use this if you don't create the
+   * event until the end of the move, but you know the original location.
+   * @param {!Coordinate} xy The location before the move,
+   *     in workspace coordinates.
    */
-  this.oldCoordinate_ = opt_comment.getXY();
+  setOldCoordinate(xy) {
+    this.oldCoordinate_ = xy;
+  }
+
+  // TODO (#1266): "Full" and "minimal" serialization.
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    if (this.oldCoordinate_) {
+      json['oldCoordinate'] = Math.round(this.oldCoordinate_.x) + ',' +
+          Math.round(this.oldCoordinate_.y);
+    }
+    if (this.newCoordinate_) {
+      json['newCoordinate'] = Math.round(this.newCoordinate_.x) + ',' +
+          Math.round(this.newCoordinate_.y);
+    }
+    return json;
+  }
 
   /**
-   * The location after the move, in workspace coordinates.
-   * @type {Coordinate}
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
    */
-  this.newCoordinate_ = null;
-};
-object.inherits(CommentMove, CommentBase);
+  fromJson(json) {
+    super.fromJson(json);
 
-/**
- * Record the comment's new location.  Called after the move.  Can only be
- * called once.
- */
-CommentMove.prototype.recordNew = function() {
-  if (!this.comment_) {
-    throw Error(
-        'Tried to record the new position of a comment on the ' +
-        'same event twice.');
-  }
-  this.newCoordinate_ = this.comment_.getXY();
-  this.comment_ = null;
-};
-
-/**
- * Type of this event.
- * @type {string}
- */
-CommentMove.prototype.type = eventUtils.COMMENT_MOVE;
-
-/**
- * Override the location before the move.  Use this if you don't create the
- * event until the end of the move, but you know the original location.
- * @param {!Coordinate} xy The location before the move,
- *     in workspace coordinates.
- */
-CommentMove.prototype.setOldCoordinate = function(xy) {
-  this.oldCoordinate_ = xy;
-};
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-// TODO (#1266): "Full" and "minimal" serialization.
-CommentMove.prototype.toJson = function() {
-  const json = CommentMove.superClass_.toJson.call(this);
-  if (this.oldCoordinate_) {
-    json['oldCoordinate'] = Math.round(this.oldCoordinate_.x) + ',' +
-        Math.round(this.oldCoordinate_.y);
-  }
-  if (this.newCoordinate_) {
-    json['newCoordinate'] = Math.round(this.newCoordinate_.x) + ',' +
-        Math.round(this.newCoordinate_.y);
-  }
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-CommentMove.prototype.fromJson = function(json) {
-  CommentMove.superClass_.fromJson.call(this, json);
-
-  if (json['oldCoordinate']) {
-    const xy = json['oldCoordinate'].split(',');
-    this.oldCoordinate_ = new Coordinate(Number(xy[0]), Number(xy[1]));
-  }
-  if (json['newCoordinate']) {
-    const xy = json['newCoordinate'].split(',');
-    this.newCoordinate_ = new Coordinate(Number(xy[0]), Number(xy[1]));
-  }
-};
-
-/**
- * Does this event record any change of state?
- * @return {boolean} False if something changed.
- */
-CommentMove.prototype.isNull = function() {
-  return Coordinate.equals(this.oldCoordinate_, this.newCoordinate_);
-};
-
-/**
- * Run a move event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-CommentMove.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  const comment = workspace.getCommentById(this.commentId);
-  if (!comment) {
-    console.warn('Can\'t move non-existent comment: ' + this.commentId);
-    return;
+    if (json['oldCoordinate']) {
+      const xy = json['oldCoordinate'].split(',');
+      this.oldCoordinate_ = new Coordinate(Number(xy[0]), Number(xy[1]));
+    }
+    if (json['newCoordinate']) {
+      const xy = json['newCoordinate'].split(',');
+      this.newCoordinate_ = new Coordinate(Number(xy[0]), Number(xy[1]));
+    }
   }
 
-  const target = forward ? this.newCoordinate_ : this.oldCoordinate_;
-  // TODO: Check if the comment is being dragged, and give up if so.
-  const current = comment.getXY();
-  comment.moveBy(target.x - current.x, target.y - current.y);
-};
+  /**
+   * Does this event record any change of state?
+   * @return {boolean} False if something changed.
+   */
+  isNull() {
+    return Coordinate.equals(this.oldCoordinate_, this.newCoordinate_);
+  }
+
+  /**
+   * Run a move event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    const comment = workspace.getCommentById(this.commentId);
+    if (!comment) {
+      console.warn('Can\'t move non-existent comment: ' + this.commentId);
+      return;
+    }
+
+    const target = forward ? this.newCoordinate_ : this.oldCoordinate_;
+    // TODO: Check if the comment is being dragged, and give up if so.
+    const current = comment.getXY();
+    comment.moveBy(target.x - current.x, target.y - current.y);
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.COMMENT_MOVE, CommentMove);
 
diff --git a/core/events/events_marker_move.js b/core/events/events_marker_move.js
index 97f473d95..214d666ee 100644
--- a/core/events/events_marker_move.js
+++ b/core/events/events_marker_move.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.MarkerMove');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {ASTNode} = goog.require('Blockly.ASTNode');
 /* eslint-disable-next-line no-unused-vars */
@@ -28,81 +27,83 @@ const {Workspace} = goog.requireType('Blockly.Workspace');
 
 /**
  * Class for a marker move event.
- * @param {?Block=} opt_block The affected block. Null if current node
- *    is of type workspace. Undefined for a blank event.
- * @param {boolean=} isCursor Whether this is a cursor event. Undefined for a
- *    blank event.
- * @param {?ASTNode=} opt_oldNode The old node the marker used to be on.
- *    Undefined for a blank event.
- * @param {!ASTNode=} opt_newNode The new node the marker is now on.
- *    Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.MarkerMove
  */
-const MarkerMove = function(opt_block, isCursor, opt_oldNode, opt_newNode) {
-  let workspaceId = opt_block ? opt_block.workspace.id : undefined;
-  if (opt_newNode && opt_newNode.getType() === ASTNode.types.WORKSPACE) {
-    workspaceId = (/** @type {!Workspace} */ (opt_newNode.getLocation())).id;
+class MarkerMove extends UiBase {
+  /**
+   * @param {?Block=} opt_block The affected block. Null if current node
+   *    is of type workspace. Undefined for a blank event.
+   * @param {boolean=} isCursor Whether this is a cursor event. Undefined for a
+   *    blank event.
+   * @param {?ASTNode=} opt_oldNode The old node the marker used to be on.
+   *    Undefined for a blank event.
+   * @param {!ASTNode=} opt_newNode The new node the marker is now on.
+   *    Undefined for a blank event.
+   * @alias Blockly.Events.MarkerMove
+   */
+  constructor(opt_block, isCursor, opt_oldNode, opt_newNode) {
+    let workspaceId = opt_block ? opt_block.workspace.id : undefined;
+    if (opt_newNode && opt_newNode.getType() === ASTNode.types.WORKSPACE) {
+      workspaceId = (/** @type {!Workspace} */ (opt_newNode.getLocation())).id;
+    }
+    super(workspaceId);
+
+    /**
+     * The workspace identifier for this event.
+     * @type {?string}
+     */
+    this.blockId = opt_block ? opt_block.id : null;
+
+    /**
+     * The old node the marker used to be on.
+     * @type {?ASTNode|undefined}
+     */
+    this.oldNode = opt_oldNode;
+
+    /**
+     * The new node the  marker is now on.
+     * @type {ASTNode|undefined}
+     */
+    this.newNode = opt_newNode;
+
+    /**
+     * Whether this is a cursor event.
+     * @type {boolean|undefined}
+     */
+    this.isCursor = isCursor;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.MARKER_MOVE;
   }
-  MarkerMove.superClass_.constructor.call(this, workspaceId);
 
   /**
-   * The workspace identifier for this event.
-   * @type {?string}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.blockId = opt_block ? opt_block.id : null;
+  toJson() {
+    const json = super.toJson();
+    json['isCursor'] = this.isCursor;
+    json['blockId'] = this.blockId;
+    json['oldNode'] = this.oldNode;
+    json['newNode'] = this.newNode;
+    return json;
+  }
 
   /**
-   * The old node the marker used to be on.
-   * @type {?ASTNode|undefined}
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
    */
-  this.oldNode = opt_oldNode;
-
-  /**
-   * The new node the  marker is now on.
-   * @type {ASTNode|undefined}
-   */
-  this.newNode = opt_newNode;
-
-  /**
-   * Whether this is a cursor event.
-   * @type {boolean|undefined}
-   */
-  this.isCursor = isCursor;
-};
-object.inherits(MarkerMove, UiBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-MarkerMove.prototype.type = eventUtils.MARKER_MOVE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-MarkerMove.prototype.toJson = function() {
-  const json = MarkerMove.superClass_.toJson.call(this);
-  json['isCursor'] = this.isCursor;
-  json['blockId'] = this.blockId;
-  json['oldNode'] = this.oldNode;
-  json['newNode'] = this.newNode;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-MarkerMove.prototype.fromJson = function(json) {
-  MarkerMove.superClass_.fromJson.call(this, json);
-  this.isCursor = json['isCursor'];
-  this.blockId = json['blockId'];
-  this.oldNode = json['oldNode'];
-  this.newNode = json['newNode'];
-};
+  fromJson(json) {
+    super.fromJson(json);
+    this.isCursor = json['isCursor'];
+    this.blockId = json['blockId'];
+    this.oldNode = json['oldNode'];
+    this.newNode = json['newNode'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.MARKER_MOVE, MarkerMove);
 
diff --git a/core/events/events_selected.js b/core/events/events_selected.js
index 7009a8549..fbf0d07a5 100644
--- a/core/events/events_selected.js
+++ b/core/events/events_selected.js
@@ -16,66 +16,67 @@
 goog.module('Blockly.Events.Selected');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 
 /**
  * Class for a selected event.
- * @param {?string=} opt_oldElementId The ID of the previously selected
- *    element. Null if no element last selected. Undefined for a blank event.
- * @param {?string=} opt_newElementId The ID of the selected element. Null if no
- *    element currently selected (deselect). Undefined for a blank event.
- * @param {string=} opt_workspaceId The workspace identifier for this event.
- *    Null if no element previously selected. Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.Selected
  */
-const Selected = function(opt_oldElementId, opt_newElementId, opt_workspaceId) {
-  Selected.superClass_.constructor.call(this, opt_workspaceId);
+class Selected extends UiBase {
+  /**
+   * @param {?string=} opt_oldElementId The ID of the previously selected
+   *    element. Null if no element last selected. Undefined for a blank event.
+   * @param {?string=} opt_newElementId The ID of the selected element. Null if
+   *     no element currently selected (deselect). Undefined for a blank event.
+   * @param {string=} opt_workspaceId The workspace identifier for this event.
+   *    Null if no element previously selected. Undefined for a blank event.
+   * @alias Blockly.Events.Selected
+   */
+  constructor(opt_oldElementId, opt_newElementId, opt_workspaceId) {
+    super(opt_workspaceId);
+
+    /**
+     * The id of the last selected element.
+     * @type {?string|undefined}
+     */
+    this.oldElementId = opt_oldElementId;
+
+    /**
+     * The id of the selected element.
+     * @type {?string|undefined}
+     */
+    this.newElementId = opt_newElementId;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.SELECTED;
+  }
 
   /**
-   * The id of the last selected element.
-   * @type {?string|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.oldElementId = opt_oldElementId;
+  toJson() {
+    const json = super.toJson();
+    json['oldElementId'] = this.oldElementId;
+    json['newElementId'] = this.newElementId;
+    return json;
+  }
 
   /**
-   * The id of the selected element.
-   * @type {?string|undefined}
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
    */
-  this.newElementId = opt_newElementId;
-};
-object.inherits(Selected, UiBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-Selected.prototype.type = eventUtils.SELECTED;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-Selected.prototype.toJson = function() {
-  const json = Selected.superClass_.toJson.call(this);
-  json['oldElementId'] = this.oldElementId;
-  json['newElementId'] = this.newElementId;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-Selected.prototype.fromJson = function(json) {
-  Selected.superClass_.fromJson.call(this, json);
-  this.oldElementId = json['oldElementId'];
-  this.newElementId = json['newElementId'];
-};
+  fromJson(json) {
+    super.fromJson(json);
+    this.oldElementId = json['oldElementId'];
+    this.newElementId = json['newElementId'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.SELECTED, Selected);
 
diff --git a/core/events/events_theme_change.js b/core/events/events_theme_change.js
index e1cba44c2..247bd0da8 100644
--- a/core/events/events_theme_change.js
+++ b/core/events/events_theme_change.js
@@ -16,55 +16,56 @@
 goog.module('Blockly.Events.ThemeChange');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 
 /**
  * Class for a theme change event.
- * @param {string=} opt_themeName The theme name. Undefined for a blank event.
- * @param {string=} opt_workspaceId The workspace identifier for this event.
- *    event. Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.ThemeChange
  */
-const ThemeChange = function(opt_themeName, opt_workspaceId) {
-  ThemeChange.superClass_.constructor.call(this, opt_workspaceId);
+class ThemeChange extends UiBase {
+  /**
+   * @param {string=} opt_themeName The theme name. Undefined for a blank event.
+   * @param {string=} opt_workspaceId The workspace identifier for this event.
+   *    event. Undefined for a blank event.
+   * @alias Blockly.Events.ThemeChange
+   */
+  constructor(opt_themeName, opt_workspaceId) {
+    super(opt_workspaceId);
+
+    /**
+     * The theme name.
+     * @type {string|undefined}
+     */
+    this.themeName = opt_themeName;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.THEME_CHANGE;
+  }
 
   /**
-   * The theme name.
-   * @type {string|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.themeName = opt_themeName;
-};
-object.inherits(ThemeChange, UiBase);
+  toJson() {
+    const json = super.toJson();
+    json['themeName'] = this.themeName;
+    return json;
+  }
 
-/**
- * Type of this event.
- * @type {string}
- */
-ThemeChange.prototype.type = eventUtils.THEME_CHANGE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-ThemeChange.prototype.toJson = function() {
-  const json = ThemeChange.superClass_.toJson.call(this);
-  json['themeName'] = this.themeName;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-ThemeChange.prototype.fromJson = function(json) {
-  ThemeChange.superClass_.fromJson.call(this, json);
-  this.themeName = json['themeName'];
-};
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.themeName = json['themeName'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.THEME_CHANGE, ThemeChange);
 
diff --git a/core/events/events_toolbox_item_select.js b/core/events/events_toolbox_item_select.js
index f2ba9bf19..6a6509316 100644
--- a/core/events/events_toolbox_item_select.js
+++ b/core/events/events_toolbox_item_select.js
@@ -16,66 +16,67 @@
 goog.module('Blockly.Events.ToolboxItemSelect');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 
 /**
  * Class for a toolbox item select event.
- * @param {?string=} opt_oldItem The previously selected toolbox item. Undefined
- *    for a blank event.
- * @param {?string=} opt_newItem The newly selected toolbox item. Undefined for
- *    a blank event.
- * @param {string=} opt_workspaceId The workspace identifier for this event.
- *    Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.ToolboxItemSelect
  */
-const ToolboxItemSelect = function(opt_oldItem, opt_newItem, opt_workspaceId) {
-  ToolboxItemSelect.superClass_.constructor.call(this, opt_workspaceId);
+class ToolboxItemSelect extends UiBase {
+  /**
+   * @param {?string=} opt_oldItem The previously selected toolbox item.
+   *     Undefined for a blank event.
+   * @param {?string=} opt_newItem The newly selected toolbox item. Undefined
+   *     for a blank event.
+   * @param {string=} opt_workspaceId The workspace identifier for this event.
+   *    Undefined for a blank event.
+   * @alias Blockly.Events.ToolboxItemSelect
+   */
+  constructor(opt_oldItem, opt_newItem, opt_workspaceId) {
+    super(opt_workspaceId);
+
+    /**
+     * The previously selected toolbox item.
+     * @type {?string|undefined}
+     */
+    this.oldItem = opt_oldItem;
+
+    /**
+     * The newly selected toolbox item.
+     * @type {?string|undefined}
+     */
+    this.newItem = opt_newItem;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.TOOLBOX_ITEM_SELECT;
+  }
 
   /**
-   * The previously selected toolbox item.
-   * @type {?string|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.oldItem = opt_oldItem;
+  toJson() {
+    const json = super.toJson();
+    json['oldItem'] = this.oldItem;
+    json['newItem'] = this.newItem;
+    return json;
+  }
 
   /**
-   * The newly selected toolbox item.
-   * @type {?string|undefined}
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
    */
-  this.newItem = opt_newItem;
-};
-object.inherits(ToolboxItemSelect, UiBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-ToolboxItemSelect.prototype.type = eventUtils.TOOLBOX_ITEM_SELECT;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-ToolboxItemSelect.prototype.toJson = function() {
-  const json = ToolboxItemSelect.superClass_.toJson.call(this);
-  json['oldItem'] = this.oldItem;
-  json['newItem'] = this.newItem;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-ToolboxItemSelect.prototype.fromJson = function(json) {
-  ToolboxItemSelect.superClass_.fromJson.call(this, json);
-  this.oldItem = json['oldItem'];
-  this.newItem = json['newItem'];
-};
+  fromJson(json) {
+    super.fromJson(json);
+    this.oldItem = json['oldItem'];
+    this.newItem = json['newItem'];
+  }
+}
 
 registry.register(
     registry.Type.EVENT, eventUtils.TOOLBOX_ITEM_SELECT, ToolboxItemSelect);
diff --git a/core/events/events_trashcan_open.js b/core/events/events_trashcan_open.js
index 21fd0d3b3..565cee307 100644
--- a/core/events/events_trashcan_open.js
+++ b/core/events/events_trashcan_open.js
@@ -16,56 +16,57 @@
 goog.module('Blockly.Events.TrashcanOpen');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 
 /**
  * Class for a trashcan open event.
- * @param {boolean=} opt_isOpen Whether the trashcan flyout is opening (false if
- *    opening). Undefined for a blank event.
- * @param {string=} opt_workspaceId The workspace identifier for this event.
- *    Undefined for a blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.TrashcanOpen
  */
-const TrashcanOpen = function(opt_isOpen, opt_workspaceId) {
-  TrashcanOpen.superClass_.constructor.call(this, opt_workspaceId);
+class TrashcanOpen extends UiBase {
+  /**
+   * @param {boolean=} opt_isOpen Whether the trashcan flyout is opening (false
+   *     if opening). Undefined for a blank event.
+   * @param {string=} opt_workspaceId The workspace identifier for this event.
+   *    Undefined for a blank event.
+   * @alias Blockly.Events.TrashcanOpen
+   */
+  constructor(opt_isOpen, opt_workspaceId) {
+    super(opt_workspaceId);
+
+    /**
+     * Whether the trashcan flyout is opening (false if closing).
+     * @type {boolean|undefined}
+     */
+    this.isOpen = opt_isOpen;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.TRASHCAN_OPEN;
+  }
 
   /**
-   * Whether the trashcan flyout is opening (false if closing).
-   * @type {boolean|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.isOpen = opt_isOpen;
-};
-object.inherits(TrashcanOpen, UiBase);
+  toJson() {
+    const json = super.toJson();
+    json['isOpen'] = this.isOpen;
+    return json;
+  }
 
-/**
- * Type of this event.
- * @type {string}
- */
-TrashcanOpen.prototype.type = eventUtils.TRASHCAN_OPEN;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-TrashcanOpen.prototype.toJson = function() {
-  const json = TrashcanOpen.superClass_.toJson.call(this);
-  json['isOpen'] = this.isOpen;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-TrashcanOpen.prototype.fromJson = function(json) {
-  TrashcanOpen.superClass_.fromJson.call(this, json);
-  this.isOpen = json['isOpen'];
-};
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.isOpen = json['isOpen'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.TRASHCAN_OPEN, TrashcanOpen);
 
diff --git a/core/events/events_ui.js b/core/events/events_ui.js
index b505d3b20..2acb2fa4e 100644
--- a/core/events/events_ui.js
+++ b/core/events/events_ui.js
@@ -18,7 +18,6 @@
 goog.module('Blockly.Events.Ui');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 /* eslint-disable-next-line no-unused-vars */
 const {Block} = goog.requireType('Blockly.Block');
@@ -27,60 +26,62 @@ const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 /**
  * Class for a UI event.
- * @param {?Block=} opt_block The affected block.  Null for UI events
- *     that do not have an associated block.  Undefined for a blank event.
- * @param {string=} opt_element One of 'selected', 'comment', 'mutatorOpen',
- *     etc.
- * @param {*=} opt_oldValue Previous value of element.
- * @param {*=} opt_newValue New value of element.
  * @extends {UiBase}
  * @deprecated December 2020. Instead use a more specific UI event.
- * @constructor
- * @alias Blockly.Events.Ui
  */
-const Ui = function(opt_block, opt_element, opt_oldValue, opt_newValue) {
-  const workspaceId = opt_block ? opt_block.workspace.id : undefined;
-  Ui.superClass_.constructor.call(this, workspaceId);
+class Ui extends UiBase {
+  /**
+   * @param {?Block=} opt_block The affected block.  Null for UI events
+   *     that do not have an associated block.  Undefined for a blank event.
+   * @param {string=} opt_element One of 'selected', 'comment', 'mutatorOpen',
+   *     etc.
+   * @param {*=} opt_oldValue Previous value of element.
+   * @param {*=} opt_newValue New value of element.
+   * @alias Blockly.Events.Ui
+   */
+  constructor(opt_block, opt_element, opt_oldValue, opt_newValue) {
+    const workspaceId = opt_block ? opt_block.workspace.id : undefined;
+    super(workspaceId);
 
-  this.blockId = opt_block ? opt_block.id : null;
-  this.element = typeof opt_element === 'undefined' ? '' : opt_element;
-  this.oldValue = typeof opt_oldValue === 'undefined' ? '' : opt_oldValue;
-  this.newValue = typeof opt_newValue === 'undefined' ? '' : opt_newValue;
-};
-object.inherits(Ui, UiBase);
+    this.blockId = opt_block ? opt_block.id : null;
+    this.element = typeof opt_element === 'undefined' ? '' : opt_element;
+    this.oldValue = typeof opt_oldValue === 'undefined' ? '' : opt_oldValue;
+    this.newValue = typeof opt_newValue === 'undefined' ? '' : opt_newValue;
 
-/**
- * Type of this event.
- * @type {string}
- */
-Ui.prototype.type = eventUtils.UI;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-Ui.prototype.toJson = function() {
-  const json = Ui.superClass_.toJson.call(this);
-  json['element'] = this.element;
-  if (this.newValue !== undefined) {
-    json['newValue'] = this.newValue;
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.UI;
   }
-  if (this.blockId) {
-    json['blockId'] = this.blockId;
-  }
-  return json;
-};
 
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-Ui.prototype.fromJson = function(json) {
-  Ui.superClass_.fromJson.call(this, json);
-  this.element = json['element'];
-  this.newValue = json['newValue'];
-  this.blockId = json['blockId'];
-};
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['element'] = this.element;
+    if (this.newValue !== undefined) {
+      json['newValue'] = this.newValue;
+    }
+    if (this.blockId) {
+      json['blockId'] = this.blockId;
+    }
+    return json;
+  }
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.element = json['element'];
+    this.newValue = json['newValue'];
+    this.blockId = json['blockId'];
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.UI, Ui);
 
diff --git a/core/events/events_ui_base.js b/core/events/events_ui_base.js
index 1618f2876..cd7ad1d2e 100644
--- a/core/events/events_ui_base.js
+++ b/core/events/events_ui_base.js
@@ -50,13 +50,13 @@ const UiBase = function(opt_workspaceId) {
 
   // UI events do not undo or redo.
   this.recordUndo = false;
+
+  /**
+   * Whether or not the event is a UI event.
+   * @type {boolean}
+   */
+  this.isUiEvent = true;
 };
 object.inherits(UiBase, Abstract);
 
-/**
- * Whether or not the event is a UI event.
- * @type {boolean}
- */
-UiBase.prototype.isUiEvent = true;
-
 exports.UiBase = UiBase;
diff --git a/core/events/events_var_create.js b/core/events/events_var_create.js
index f924fd98d..0de02d99c 100644
--- a/core/events/events_var_create.js
+++ b/core/events/events_var_create.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.VarCreate');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {VarBase} = goog.require('Blockly.Events.VarBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -25,62 +24,65 @@ const {VariableModel} = goog.requireType('Blockly.VariableModel');
 
 /**
  * Class for a variable creation event.
- * @param {!VariableModel=} opt_variable The created variable. Undefined
- *     for a blank event.
  * @extends {VarBase}
- * @constructor
- * @alias Blockly.Events.VarCreate
  */
-const VarCreate = function(opt_variable) {
-  VarCreate.superClass_.constructor.call(this, opt_variable);
-  if (!opt_variable) {
-    return;  // Blank event to be populated by fromJson.
+class VarCreate extends VarBase {
+  /**
+   * @param {!VariableModel=} opt_variable The created variable. Undefined
+   *     for a blank event.
+   * @alias Blockly.Events.VarCreate
+   */
+  constructor(opt_variable) {
+    super(opt_variable);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.VAR_CREATE;
+
+    if (!opt_variable) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    this.varType = opt_variable.type;
+    this.varName = opt_variable.name;
   }
 
-  this.varType = opt_variable.type;
-  this.varName = opt_variable.name;
-};
-object.inherits(VarCreate, VarBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-VarCreate.prototype.type = eventUtils.VAR_CREATE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-VarCreate.prototype.toJson = function() {
-  const json = VarCreate.superClass_.toJson.call(this);
-  json['varType'] = this.varType;
-  json['varName'] = this.varName;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-VarCreate.prototype.fromJson = function(json) {
-  VarCreate.superClass_.fromJson.call(this, json);
-  this.varType = json['varType'];
-  this.varName = json['varName'];
-};
-
-/**
- * Run a variable creation event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-VarCreate.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  if (forward) {
-    workspace.createVariable(this.varName, this.varType, this.varId);
-  } else {
-    workspace.deleteVariableById(this.varId);
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['varType'] = this.varType;
+    json['varName'] = this.varName;
+    return json;
   }
-};
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.varType = json['varType'];
+    this.varName = json['varName'];
+  }
+
+  /**
+   * Run a variable creation event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    if (forward) {
+      workspace.createVariable(this.varName, this.varType, this.varId);
+    } else {
+      workspace.deleteVariableById(this.varId);
+    }
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.VAR_CREATE, VarCreate);
 
diff --git a/core/events/events_var_delete.js b/core/events/events_var_delete.js
index 2c8b34fb2..3c0eb2a58 100644
--- a/core/events/events_var_delete.js
+++ b/core/events/events_var_delete.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.VarDelete');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {VarBase} = goog.require('Blockly.Events.VarBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -25,62 +24,65 @@ const {VariableModel} = goog.requireType('Blockly.VariableModel');
 
 /**
  * Class for a variable deletion event.
- * @param {!VariableModel=} opt_variable The deleted variable. Undefined
- *     for a blank event.
  * @extends {VarBase}
- * @constructor
- * @alias Blockly.Events.VarDelete
  */
-const VarDelete = function(opt_variable) {
-  VarDelete.superClass_.constructor.call(this, opt_variable);
-  if (!opt_variable) {
-    return;  // Blank event to be populated by fromJson.
+class VarDelete extends VarBase {
+  /**
+   * @param {!VariableModel=} opt_variable The deleted variable. Undefined
+   *     for a blank event.
+   * @alias Blockly.Events.VarDelete
+   */
+  constructor(opt_variable) {
+    super(opt_variable);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.VAR_DELETE;
+
+    if (!opt_variable) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    this.varType = opt_variable.type;
+    this.varName = opt_variable.name;
   }
 
-  this.varType = opt_variable.type;
-  this.varName = opt_variable.name;
-};
-object.inherits(VarDelete, VarBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-VarDelete.prototype.type = eventUtils.VAR_DELETE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-VarDelete.prototype.toJson = function() {
-  const json = VarDelete.superClass_.toJson.call(this);
-  json['varType'] = this.varType;
-  json['varName'] = this.varName;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-VarDelete.prototype.fromJson = function(json) {
-  VarDelete.superClass_.fromJson.call(this, json);
-  this.varType = json['varType'];
-  this.varName = json['varName'];
-};
-
-/**
- * Run a variable deletion event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-VarDelete.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  if (forward) {
-    workspace.deleteVariableById(this.varId);
-  } else {
-    workspace.createVariable(this.varName, this.varType, this.varId);
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['varType'] = this.varType;
+    json['varName'] = this.varName;
+    return json;
   }
-};
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.varType = json['varType'];
+    this.varName = json['varName'];
+  }
+
+  /**
+   * Run a variable deletion event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    if (forward) {
+      workspace.deleteVariableById(this.varId);
+    } else {
+      workspace.createVariable(this.varName, this.varType, this.varId);
+    }
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.VAR_DELETE, VarDelete);
 
diff --git a/core/events/events_var_rename.js b/core/events/events_var_rename.js
index 97d8fd882..17d3774e5 100644
--- a/core/events/events_var_rename.js
+++ b/core/events/events_var_rename.js
@@ -16,7 +16,6 @@
 goog.module('Blockly.Events.VarRename');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {VarBase} = goog.require('Blockly.Events.VarBase');
 /* eslint-disable-next-line no-unused-vars */
@@ -25,63 +24,66 @@ const {VariableModel} = goog.requireType('Blockly.VariableModel');
 
 /**
  * Class for a variable rename event.
- * @param {!VariableModel=} opt_variable The renamed variable. Undefined
- *     for a blank event.
- * @param {string=} newName The new name the variable will be changed to.
  * @extends {VarBase}
- * @constructor
- * @alias Blockly.Events.VarRename
  */
-const VarRename = function(opt_variable, newName) {
-  VarRename.superClass_.constructor.call(this, opt_variable);
-  if (!opt_variable) {
-    return;  // Blank event to be populated by fromJson.
+class VarRename extends VarBase {
+  /**
+   * @param {!VariableModel=} opt_variable The renamed variable. Undefined
+   *     for a blank event.
+   * @param {string=} newName The new name the variable will be changed to.
+   * @alias Blockly.Events.VarRename
+   */
+  constructor(opt_variable, newName) {
+    super(opt_variable);
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.VAR_RENAME;
+
+    if (!opt_variable) {
+      return;  // Blank event to be populated by fromJson.
+    }
+
+    this.oldName = opt_variable.name;
+    this.newName = typeof newName === 'undefined' ? '' : newName;
   }
 
-  this.oldName = opt_variable.name;
-  this.newName = typeof newName === 'undefined' ? '' : newName;
-};
-object.inherits(VarRename, VarBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-VarRename.prototype.type = eventUtils.VAR_RENAME;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-VarRename.prototype.toJson = function() {
-  const json = VarRename.superClass_.toJson.call(this);
-  json['oldName'] = this.oldName;
-  json['newName'] = this.newName;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-VarRename.prototype.fromJson = function(json) {
-  VarRename.superClass_.fromJson.call(this, json);
-  this.oldName = json['oldName'];
-  this.newName = json['newName'];
-};
-
-/**
- * Run a variable rename event.
- * @param {boolean} forward True if run forward, false if run backward (undo).
- */
-VarRename.prototype.run = function(forward) {
-  const workspace = this.getEventWorkspace_();
-  if (forward) {
-    workspace.renameVariableById(this.varId, this.newName);
-  } else {
-    workspace.renameVariableById(this.varId, this.oldName);
+  /**
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
+   */
+  toJson() {
+    const json = super.toJson();
+    json['oldName'] = this.oldName;
+    json['newName'] = this.newName;
+    return json;
   }
-};
+
+  /**
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
+   */
+  fromJson(json) {
+    super.fromJson(json);
+    this.oldName = json['oldName'];
+    this.newName = json['newName'];
+  }
+
+  /**
+   * Run a variable rename event.
+   * @param {boolean} forward True if run forward, false if run backward (undo).
+   */
+  run(forward) {
+    const workspace = this.getEventWorkspace_();
+    if (forward) {
+      workspace.renameVariableById(this.varId, this.newName);
+    } else {
+      workspace.renameVariableById(this.varId, this.oldName);
+    }
+  }
+}
 
 registry.register(registry.Type.EVENT, eventUtils.VAR_RENAME, VarRename);
 
diff --git a/core/events/events_viewport.js b/core/events/events_viewport.js
index 71ac3d3c7..bde96edf8 100644
--- a/core/events/events_viewport.js
+++ b/core/events/events_viewport.js
@@ -16,89 +16,90 @@
 goog.module('Blockly.Events.ViewportChange');
 
 const eventUtils = goog.require('Blockly.Events.utils');
-const object = goog.require('Blockly.utils.object');
 const registry = goog.require('Blockly.registry');
 const {UiBase} = goog.require('Blockly.Events.UiBase');
 
 
 /**
  * Class for a viewport change event.
- * @param {number=} opt_top Top-edge of the visible portion of the workspace,
- *    relative to the workspace origin. Undefined for a blank event.
- * @param {number=} opt_left Left-edge of the visible portion of the workspace,
- *    relative to the workspace origin. Undefined for a blank event.
- * @param {number=} opt_scale The scale of the workspace. Undefined for a blank
- *    event.
- * @param {string=} opt_workspaceId The workspace identifier for this event.
- *    Undefined for a blank event.
- * @param {number=} opt_oldScale The old scale of the workspace. Undefined for a
- *    blank event.
  * @extends {UiBase}
- * @constructor
- * @alias Blockly.Events.ViewportChange
  */
-const ViewportChange = function(
-    opt_top, opt_left, opt_scale, opt_workspaceId, opt_oldScale) {
-  ViewportChange.superClass_.constructor.call(this, opt_workspaceId);
+class ViewportChange extends UiBase {
+  /**
+   * @param {number=} opt_top Top-edge of the visible portion of the workspace,
+   *    relative to the workspace origin. Undefined for a blank event.
+   * @param {number=} opt_left Left-edge of the visible portion of the
+   *     workspace relative to the workspace origin. Undefined for a blank
+   *     event.
+   * @param {number=} opt_scale The scale of the workspace. Undefined for a
+   *     blank event.
+   * @param {string=} opt_workspaceId The workspace identifier for this event.
+   *    Undefined for a blank event.
+   * @param {number=} opt_oldScale The old scale of the workspace. Undefined for
+   *     a blank event.
+   * @alias Blockly.Events.ViewportChange
+   */
+  constructor(opt_top, opt_left, opt_scale, opt_workspaceId, opt_oldScale) {
+    super(opt_workspaceId);
+
+    /**
+     * Top-edge of the visible portion of the workspace, relative to the
+     * workspace origin.
+     * @type {number|undefined}
+     */
+    this.viewTop = opt_top;
+
+    /**
+     * Left-edge of the visible portion of the workspace, relative to the
+     * workspace origin.
+     * @type {number|undefined}
+     */
+    this.viewLeft = opt_left;
+
+    /**
+     * The scale of the workspace.
+     * @type {number|undefined}
+     */
+    this.scale = opt_scale;
+
+    /**
+     * The old scale of the workspace.
+     * @type {number|undefined}
+     */
+    this.oldScale = opt_oldScale;
+
+    /**
+     * Type of this event.
+     * @type {string}
+     */
+    this.type = eventUtils.VIEWPORT_CHANGE;
+  }
 
   /**
-   * Top-edge of the visible portion of the workspace, relative to the workspace
-   * origin.
-   * @type {number|undefined}
+   * Encode the event as JSON.
+   * @return {!Object} JSON representation.
    */
-  this.viewTop = opt_top;
+  toJson() {
+    const json = super.toJson();
+    json['viewTop'] = this.viewTop;
+    json['viewLeft'] = this.viewLeft;
+    json['scale'] = this.scale;
+    json['oldScale'] = this.oldScale;
+    return json;
+  }
 
   /**
-   * Left-edge of the visible portion of the workspace, relative to the
-   * workspace origin.
-   * @type {number|undefined}
+   * Decode the JSON event.
+   * @param {!Object} json JSON representation.
    */
-  this.viewLeft = opt_left;
-
-  /**
-   * The scale of the workspace.
-   * @type {number|undefined}
-   */
-  this.scale = opt_scale;
-
-  /**
-   * The old scale of the workspace.
-   * @type {number|undefined}
-   */
-  this.oldScale = opt_oldScale;
-};
-object.inherits(ViewportChange, UiBase);
-
-/**
- * Type of this event.
- * @type {string}
- */
-ViewportChange.prototype.type = eventUtils.VIEWPORT_CHANGE;
-
-/**
- * Encode the event as JSON.
- * @return {!Object} JSON representation.
- */
-ViewportChange.prototype.toJson = function() {
-  const json = ViewportChange.superClass_.toJson.call(this);
-  json['viewTop'] = this.viewTop;
-  json['viewLeft'] = this.viewLeft;
-  json['scale'] = this.scale;
-  json['oldScale'] = this.oldScale;
-  return json;
-};
-
-/**
- * Decode the JSON event.
- * @param {!Object} json JSON representation.
- */
-ViewportChange.prototype.fromJson = function(json) {
-  ViewportChange.superClass_.fromJson.call(this, json);
-  this.viewTop = json['viewTop'];
-  this.viewLeft = json['viewLeft'];
-  this.scale = json['scale'];
-  this.oldScale = json['oldScale'];
-};
+  fromJson(json) {
+    super.fromJson(json);
+    this.viewTop = json['viewTop'];
+    this.viewLeft = json['viewLeft'];
+    this.scale = json['scale'];
+    this.oldScale = json['oldScale'];
+  }
+}
 
 registry.register(
     registry.Type.EVENT, eventUtils.VIEWPORT_CHANGE, ViewportChange);
diff --git a/tests/deps.js b/tests/deps.js
index 55bfc76b6..ab5c32064 100644
--- a/tests/deps.js
+++ b/tests/deps.js
@@ -40,30 +40,30 @@ goog.addDependency('../../core/dropdowndiv.js', ['Blockly.DropDownDiv'], ['Block
 goog.addDependency('../../core/events/events.js', ['Blockly.Events'], ['Blockly.Events.Abstract', 'Blockly.Events.BlockBase', 'Blockly.Events.BlockChange', 'Blockly.Events.BlockCreate', 'Blockly.Events.BlockDelete', 'Blockly.Events.BlockDrag', 'Blockly.Events.BlockMove', 'Blockly.Events.BubbleOpen', 'Blockly.Events.Click', 'Blockly.Events.CommentBase', 'Blockly.Events.CommentChange', 'Blockly.Events.CommentCreate', 'Blockly.Events.CommentDelete', 'Blockly.Events.CommentMove', 'Blockly.Events.FinishedLoading', 'Blockly.Events.MarkerMove', 'Blockly.Events.Selected', 'Blockly.Events.ThemeChange', 'Blockly.Events.ToolboxItemSelect', 'Blockly.Events.TrashcanOpen', 'Blockly.Events.Ui', 'Blockly.Events.UiBase', 'Blockly.Events.VarBase', 'Blockly.Events.VarCreate', 'Blockly.Events.VarDelete', 'Blockly.Events.VarRename', 'Blockly.Events.ViewportChange', 'Blockly.Events.utils', 'Blockly.utils.deprecation'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_abstract.js', ['Blockly.Events.Abstract'], ['Blockly.Events.utils'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_block_base.js', ['Blockly.Events.BlockBase'], ['Blockly.Events.Abstract', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_block_change.js', ['Blockly.Events.BlockChange'], ['Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_block_create.js', ['Blockly.Events.BlockCreate'], ['Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry', 'Blockly.serialization.blocks', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_block_delete.js', ['Blockly.Events.BlockDelete'], ['Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry', 'Blockly.serialization.blocks', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_block_drag.js', ['Blockly.Events.BlockDrag'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_block_move.js', ['Blockly.Events.BlockMove'], ['Blockly.ConnectionType', 'Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.Coordinate', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_block_change.js', ['Blockly.Events.BlockChange'], ['Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_block_create.js', ['Blockly.Events.BlockCreate'], ['Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry', 'Blockly.serialization.blocks'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_block_delete.js', ['Blockly.Events.BlockDelete'], ['Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry', 'Blockly.serialization.blocks'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_block_drag.js', ['Blockly.Events.BlockDrag'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_block_move.js', ['Blockly.Events.BlockMove'], ['Blockly.ConnectionType', 'Blockly.Events.BlockBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.Coordinate'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_bubble_open.js', ['Blockly.Events.BubbleOpen'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_click.js', ['Blockly.Events.Click'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_click.js', ['Blockly.Events.Click'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_comment_base.js', ['Blockly.Events.CommentBase'], ['Blockly.Events.Abstract', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.utils.object', 'Blockly.utils.xml'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_comment_change.js', ['Blockly.Events.CommentChange'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_comment_create.js', ['Blockly.Events.CommentCreate'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_comment_delete.js', ['Blockly.Events.CommentDelete'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_comment_move.js', ['Blockly.Events.CommentMove'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.Coordinate', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_marker_move.js', ['Blockly.Events.MarkerMove'], ['Blockly.ASTNode', 'Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_selected.js', ['Blockly.Events.Selected'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_theme_change.js', ['Blockly.Events.ThemeChange'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_toolbox_item_select.js', ['Blockly.Events.ToolboxItemSelect'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_trashcan_open.js', ['Blockly.Events.TrashcanOpen'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_ui.js', ['Blockly.Events.Ui'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_comment_change.js', ['Blockly.Events.CommentChange'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_comment_create.js', ['Blockly.Events.CommentCreate'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.Xml', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_comment_delete.js', ['Blockly.Events.CommentDelete'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_comment_move.js', ['Blockly.Events.CommentMove'], ['Blockly.Events.CommentBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.Coordinate'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_marker_move.js', ['Blockly.Events.MarkerMove'], ['Blockly.ASTNode', 'Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_selected.js', ['Blockly.Events.Selected'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_theme_change.js', ['Blockly.Events.ThemeChange'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_toolbox_item_select.js', ['Blockly.Events.ToolboxItemSelect'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_trashcan_open.js', ['Blockly.Events.TrashcanOpen'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_ui.js', ['Blockly.Events.Ui'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_ui_base.js', ['Blockly.Events.UiBase'], ['Blockly.Events.Abstract', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_var_base.js', ['Blockly.Events.VarBase'], ['Blockly.Events.Abstract', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_var_create.js', ['Blockly.Events.VarCreate'], ['Blockly.Events.VarBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_var_delete.js', ['Blockly.Events.VarDelete'], ['Blockly.Events.VarBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_var_rename.js', ['Blockly.Events.VarRename'], ['Blockly.Events.VarBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/events/events_viewport.js', ['Blockly.Events.ViewportChange'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_var_create.js', ['Blockly.Events.VarCreate'], ['Blockly.Events.VarBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_var_delete.js', ['Blockly.Events.VarDelete'], ['Blockly.Events.VarBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_var_rename.js', ['Blockly.Events.VarRename'], ['Blockly.Events.VarBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/events/events_viewport.js', ['Blockly.Events.ViewportChange'], ['Blockly.Events.UiBase', 'Blockly.Events.utils', 'Blockly.registry'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/utils.js', ['Blockly.Events.utils'], ['Blockly.registry', 'Blockly.utils.idGenerator'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/workspace_events.js', ['Blockly.Events.FinishedLoading'], ['Blockly.Events.Abstract', 'Blockly.Events.utils', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/extensions.js', ['Blockly.Extensions'], ['Blockly.utils.parsing'], {'lang': 'es6', 'module': 'goog'});
diff --git a/tests/deps.mocha.js b/tests/deps.mocha.js
index 4be80abef..a686fdda7 100644
--- a/tests/deps.mocha.js
+++ b/tests/deps.mocha.js
@@ -1,10 +1,10 @@
 goog.addDependency('../../tests/mocha/.mocharc.js', [], []);
 goog.addDependency('../../tests/mocha/astnode_test.js', ['Blockly.test.astNode'], ['Blockly.ASTNode', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/block_change_event_test.js', ['Blockly.test.blockChangeEvent'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/block_create_event_test.js', ['Blockly.test.blockCreateEvent'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/block_create_event_test.js', ['Blockly.test.blockCreateEvent'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/block_json_test.js', ['Blockly.test.blockJson'], ['Blockly.Input'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/block_test.js', ['Blockly.test.blocks'], ['Blockly.ConnectionType', 'Blockly.Events.utils', 'Blockly.blocks', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/comment_test.js', ['Blockly.test.comments'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/comment_test.js', ['Blockly.test.comments'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/connection_checker_test.js', ['Blockly.test.connectionChecker'], ['Blockly.ConnectionType', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/connection_db_test.js', ['Blockly.test.connectionDb'], ['Blockly.ConnectionType', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/connection_test.js', ['Blockly.test.connection'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
@@ -28,10 +28,10 @@ goog.addDependency('../../tests/mocha/field_textinput_test.js', ['Blockly.test.f
 goog.addDependency('../../tests/mocha/field_variable_test.js', ['Blockly.test.fieldVariable'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/flyout_test.js', ['Blockly.test.flyout'], ['Blockly.test.helpers', 'Blockly.test.toolboxHelpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/generator_test.js', ['Blockly.test.generator'], ['Blockly.Dart', 'Blockly.JavaScript', 'Blockly.Lua', 'Blockly.PHP', 'Blockly.Python', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/gesture_test.js', ['Blockly.test.gesture'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/gesture_test.js', ['Blockly.test.gesture'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/input_test.js', ['Blockly.test.input'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/insertion_marker_test.js', ['Blockly.test.insertionMarker'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/jso_deserialization_test.js', ['Blockly.test.jsoDeserialization'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/jso_deserialization_test.js', ['Blockly.test.jsoDeserialization'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/jso_serialization_test.js', ['Blockly.test.jsoSerialization'], ['Blockly.test.helpers'], {'lang': 'es8', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/json_test.js', ['Blockly.test.json'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/keydown_test.js', ['Blockly.test.keydown'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
@@ -46,7 +46,7 @@ goog.addDependency('../../tests/mocha/run_mocha_tests_in_browser.js', [], [], {'
 goog.addDependency('../../tests/mocha/serializer_test.js', ['Blockly.test.serialization'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/shortcut_registry_test.js', ['Blockly.test.shortcutRegistry'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/test_helpers.js', ['Blockly.test.helpers'], ['Blockly.Events.utils', 'Blockly.blocks', 'Blockly.utils.KeyCodes'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/theme_test.js', ['Blockly.test.theme'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/theme_test.js', ['Blockly.test.theme'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/toolbox_helper.js', ['Blockly.test.toolboxHelpers'], [], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/toolbox_test.js', ['Blockly.test.toolbox'], ['Blockly.test.helpers', 'Blockly.test.toolboxHelpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/tooltip_test.js', ['Blockly.test.tooltip'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
@@ -58,7 +58,7 @@ goog.addDependency('../../tests/mocha/variables_test.js', ['Blockly.test.variabl
 goog.addDependency('../../tests/mocha/widget_div_test.js', ['Blockly.test.widgetDiv'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/workspace_comment_test.js', ['Blockly.test.workspaceComment'], ['Blockly.WorkspaceComment', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/workspace_helpers.js', ['Blockly.test.workspaceHelpers'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/workspace_svg_test.js', ['Blockly.test.workspaceSvg'], ['Blockly.test.helpers', 'Blockly.test.workspaceHelpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/workspace_svg_test.js', ['Blockly.test.workspaceSvg'], ['Blockly.Events.utils', 'Blockly.test.helpers', 'Blockly.test.workspaceHelpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/workspace_test.js', ['Blockly.test.workspace'], ['Blockly.test.helpers', 'Blockly.test.workspaceHelpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/xml_test.js', ['Blockly.test.xml'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/zoom_controls_test.js', ['Blockly.test.zoomControls'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/zoom_controls_test.js', ['Blockly.test.zoomControls'], ['Blockly.Events.utils', 'Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
diff --git a/tests/mocha/block_create_event_test.js b/tests/mocha/block_create_event_test.js
index 91a84af3e..69debed96 100644
--- a/tests/mocha/block_create_event_test.js
+++ b/tests/mocha/block_create_event_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.blockCreateEvent');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, sharedTestSetup, sharedTestTeardown} = goog.require('Blockly.test.helpers');
 
 
@@ -48,7 +49,7 @@ suite('Block Create Event', function() {
     assertEventFired(
         this.eventsFireStub,
         Blockly.Events.BlockCreate,
-        {'recordUndo': false},
+        {'recordUndo': false, 'type': eventUtils.BLOCK_CREATE},
         this.workspace.id,
         'shadowId');
     const calls = this.eventsFireStub.getCalls();
diff --git a/tests/mocha/comment_test.js b/tests/mocha/comment_test.js
index fa3a86d6b..94a496637 100644
--- a/tests/mocha/comment_test.js
+++ b/tests/mocha/comment_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.comments');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, sharedTestSetup, sharedTestTeardown} = goog.require('Blockly.test.helpers');
 
 
@@ -54,7 +55,7 @@ suite('Comments', function() {
       assertEditable(this.comment);
       assertEventFired(
           this.eventsFireStub, Blockly.Events.BubbleOpen,
-          {bubbleType: 'comment', isOpen: true}, this.workspace.id,
+          {bubbleType: 'comment', isOpen: true, type: eventUtils.BUBBLE_OPEN}, this.workspace.id,
           this.block.id);
     });
     test('Not Editable', function() {
@@ -66,8 +67,8 @@ suite('Comments', function() {
       assertNotEditable(this.comment);
       assertEventFired(
           this.eventsFireStub, Blockly.Events.BubbleOpen,
-          {bubbleType: 'comment', isOpen: true}, this.workspace.id,
-          this.block.id);
+          {bubbleType: 'comment', isOpen: true, type: eventUtils.BUBBLE_OPEN},
+          this.workspace.id, this.block.id);
     });
     test('Editable -> Not Editable', function() {
       this.comment.setVisible(true);
@@ -79,8 +80,8 @@ suite('Comments', function() {
       assertNotEditable(this.comment);
       assertEventFired(
           this.eventsFireStub, Blockly.Events.BubbleOpen,
-          {bubbleType: 'comment', isOpen: true}, this.workspace.id,
-          this.block.id);
+          {bubbleType: 'comment', isOpen: true, type: eventUtils.BUBBLE_OPEN},
+          this.workspace.id, this.block.id);
     });
     test('Not Editable -> Editable', function() {
       const editableStub = sinon.stub(this.block, 'isEditable').returns(false);
@@ -94,8 +95,8 @@ suite('Comments', function() {
       assertEditable(this.comment);
       assertEventFired(
           this.eventsFireStub, Blockly.Events.BubbleOpen,
-          {bubbleType: 'comment', isOpen: true}, this.workspace.id,
-          this.block.id);
+          {bubbleType: 'comment', isOpen: true, type: eventUtils.BUBBLE_OPEN},
+          this.workspace.id, this.block.id);
     });
   });
   suite('Set/Get Bubble Size', function() {
diff --git a/tests/mocha/gesture_test.js b/tests/mocha/gesture_test.js
index 8ecaee0de..16a6cadda 100644
--- a/tests/mocha/gesture_test.js
+++ b/tests/mocha/gesture_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.gesture');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, assertEventNotFired, defineBasicBlockWithField, dispatchPointerEvent, sharedTestSetup, sharedTestTeardown} = goog.require('Blockly.test.helpers');
 
 
@@ -34,8 +35,8 @@ suite('Gesture', function() {
 
 
     assertEventFired(eventsFireStub, Blockly.Events.Selected,
-        {oldElementId: null, newElementId: block.id}, fieldWorkspace.id);
-    assertEventNotFired(eventsFireStub, Blockly.Events.Click, {});
+        {oldElementId: null, newElementId: block.id, type: eventUtils.SELECTED}, fieldWorkspace.id);
+    assertEventNotFired(eventsFireStub, Blockly.Events.Click, {type: eventUtils.CLICK});
   }
 
   function getTopFlyoutBlock(flyout) {
diff --git a/tests/mocha/jso_deserialization_test.js b/tests/mocha/jso_deserialization_test.js
index 3a0d51f8e..02eace4af 100644
--- a/tests/mocha/jso_deserialization_test.js
+++ b/tests/mocha/jso_deserialization_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.jsoDeserialization');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, sharedTestSetup, sharedTestTeardown, workspaceTeardown} = goog.require('Blockly.test.helpers');
 
 
@@ -38,7 +39,7 @@ suite('JSO Deserialization', function() {
         assertEventFired(
             this.eventsFireStub,
             Blockly.Events.FinishedLoading,
-            {},
+            {type: eventUtils.FINISHED_LOADING},
             this.workspace.id);
       });
 
@@ -58,9 +59,8 @@ suite('JSO Deserialization', function() {
         Blockly.Events.setGroup('my group');
         Blockly.serialization.workspaces.load(state, this.workspace);
         assertEventFired(
-            this.eventsFireStub,
-            Blockly.Events.FinishedLoading,
-            {'group': 'my group'},
+            this.eventsFireStub, Blockly.Events.FinishedLoading,
+            {'group': 'my group', "type": eventUtils.FINISHED_LOADING},
             this.workspace.id);
       });
 
@@ -107,13 +107,12 @@ suite('JSO Deserialization', function() {
         };
         Blockly.serialization.workspaces.load(state, this.workspace);
         assertEventFired(
-            this.eventsFireStub,
-            Blockly.Events.VarCreate,
-            {
+            this.eventsFireStub, Blockly.Events.VarCreate, {
               'varName': 'test',
               'varId': 'testId',
               'varType': '',
               'recordUndo': false,
+              "type": eventUtils.VAR_CREATE,
             },
             this.workspace.id);
       });
@@ -129,13 +128,12 @@ suite('JSO Deserialization', function() {
         };
         Blockly.serialization.workspaces.load(state, this.workspace, {recordUndo: true});
         assertEventFired(
-            this.eventsFireStub,
-            Blockly.Events.VarCreate,
-            {
+            this.eventsFireStub, Blockly.Events.VarCreate, {
               'varName': 'test',
               'varId': 'testId',
               'varType': '',
               'recordUndo': true,
+              "type": eventUtils.VAR_CREATE,
             },
             this.workspace.id);
       });
@@ -152,13 +150,12 @@ suite('JSO Deserialization', function() {
         Blockly.Events.setGroup('my group');
         Blockly.serialization.workspaces.load(state, this.workspace);
         assertEventFired(
-            this.eventsFireStub,
-            Blockly.Events.VarCreate,
-            {
+            this.eventsFireStub, Blockly.Events.VarCreate, {
               'varName': 'test',
               'varId': 'testId',
               'varType': '',
               'group': 'my group',
+              "type": eventUtils.VAR_CREATE,
             },
             this.workspace.id);
       });
@@ -216,9 +213,12 @@ suite('JSO Deserialization', function() {
         }, 0);
         chai.assert.equal(count, 1);
         assertEventFired(
-            this.eventsFireStub,
-            Blockly.Events.VarCreate,
-            {'varName': 'test', 'varId': 'testId', 'varType': ''},
+            this.eventsFireStub, Blockly.Events.VarCreate, {
+              'varName': 'test',
+              'varId': 'testId',
+              'varType': '',
+              "type": eventUtils.VAR_CREATE,
+            },
             this.workspace.id);
       });
     });
@@ -242,7 +242,7 @@ suite('JSO Deserialization', function() {
           assertEventFired(
               this.eventsFireStub,
               Blockly.Events.BlockCreate,
-              {'recordUndo': false},
+              {'recordUndo': false, "type": eventUtils.BLOCK_CREATE},
               this.workspace.id,
               'testId');
         });
@@ -264,7 +264,7 @@ suite('JSO Deserialization', function() {
           assertEventFired(
               this.eventsFireStub,
               Blockly.Events.BlockCreate,
-              {'recordUndo': true},
+              {'recordUndo': true, "type": eventUtils.BLOCK_CREATE},
               this.workspace.id,
               'testId');
         });
@@ -287,7 +287,7 @@ suite('JSO Deserialization', function() {
           assertEventFired(
               this.eventsFireStub,
               Blockly.Events.BlockCreate,
-              {'group': 'my group'},
+              {'group': 'my group', "type": eventUtils.BLOCK_CREATE},
               this.workspace.id,
               'testId');
         });
@@ -348,7 +348,7 @@ suite('JSO Deserialization', function() {
           assertEventFired(
               this.eventsFireStub,
               Blockly.Events.BlockCreate,
-              {},
+              {type: eventUtils.BLOCK_CREATE},
               this.workspace.id,
               'id1');
         });
@@ -383,7 +383,7 @@ suite('JSO Deserialization', function() {
           assertEventFired(
               this.eventsFireStub,
               Blockly.Events.BlockCreate,
-              {'recordUndo': true},
+              {'recordUndo': true, "type": eventUtils.BLOCK_CREATE},
               this.workspace.id,
               'testId');
         });
@@ -400,7 +400,7 @@ suite('JSO Deserialization', function() {
           assertEventFired(
               this.eventsFireStub,
               Blockly.Events.BlockCreate,
-              {'group': 'my group'},
+              {'group': 'my group', "type": eventUtils.BLOCK_CREATE},
               this.workspace.id,
               'testId');
         });
@@ -662,7 +662,7 @@ suite('JSO Deserialization', function() {
 
     Blockly.serialization.workspaces.load(
         {'first': {}, 'third': {}, 'second': {}}, this.workspace);
-    
+
     Blockly.serialization.registry.unregister('first');
     Blockly.serialization.registry.unregister('second');
     Blockly.serialization.registry.unregister('third');
diff --git a/tests/mocha/test_helpers.js b/tests/mocha/test_helpers.js
index 9a404e629..4f8ab2eaf 100644
--- a/tests/mocha/test_helpers.js
+++ b/tests/mocha/test_helpers.js
@@ -401,7 +401,6 @@ exports.assertEventEquals = assertEventEquals;
 function assertEventFired(spy, instanceType, expectedProperties,
     expectedWorkspaceId, expectedBlockId) {
   expectedProperties = Object.assign({
-    type: instanceType.prototype.type,
     workspaceId: expectedWorkspaceId,
     blockId: expectedBlockId,
   }, expectedProperties);
@@ -423,7 +422,6 @@ exports.assertEventFired = assertEventFired;
  */
 function assertEventNotFired(spy, instanceType, expectedProperties,
     expectedWorkspaceId, expectedBlockId) {
-  expectedProperties.type = instanceType.prototype.type;
   if (expectedWorkspaceId !== undefined) {
     expectedProperties.workspaceId = expectedWorkspaceId;
   }
diff --git a/tests/mocha/theme_test.js b/tests/mocha/theme_test.js
index 5c8d5d24e..fa9480624 100644
--- a/tests/mocha/theme_test.js
+++ b/tests/mocha/theme_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.theme');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, sharedTestSetup, sharedTestTeardown, workspaceTeardown} = goog.require('Blockly.test.helpers');
 
 
@@ -146,7 +147,7 @@ suite('Theme', function() {
 
       assertEventFired(
           this.eventsFireStub, Blockly.Events.ThemeChange,
-          {themeName: 'themeName'}, workspace.id);
+          {themeName: 'themeName', type: eventUtils.THEME_CHANGE}, workspace.id);
     } finally {
       workspaceTeardown.call(this, workspace);
     }
diff --git a/tests/mocha/trashcan_test.js b/tests/mocha/trashcan_test.js
index fc4550b77..d82f60699 100644
--- a/tests/mocha/trashcan_test.js
+++ b/tests/mocha/trashcan_test.js
@@ -6,8 +6,8 @@
 
 goog.module('Blockly.test.trashcan');
 
-const {assertEventFired, assertEventNotFired, defineBasicBlockWithField, defineRowBlock, defineStatementBlock, defineStackBlock, defineMutatorBlocks, sharedTestSetup, sharedTestTeardown, simulateClick} = goog.require('Blockly.test.helpers');
 const eventUtils = goog.require('Blockly.Events.utils');
+const {assertEventFired, assertEventNotFired, defineBasicBlockWithField, defineRowBlock, defineStatementBlock, defineStackBlock, defineMutatorBlocks, sharedTestSetup, sharedTestTeardown, simulateClick} = goog.require('Blockly.test.helpers');
 
 
 suite("Trashcan", function() {
@@ -77,9 +77,9 @@ suite("Trashcan", function() {
       simulateClick(this.trashcan.svgGroup_);
 
       assertEventNotFired(
-          this.eventsFireStub, Blockly.Events.TrashcanOpen, {});
+          this.eventsFireStub, Blockly.Events.TrashcanOpen, {type: eventUtils.CLICK});
       assertEventFired(
-          this.eventsFireStub, Blockly.Events.Click, {targetType: 'workspace'},
+          this.eventsFireStub, Blockly.Events.Click, {targetType: 'workspace', type: eventUtils.CLICK},
           this.workspace.id, null);
     });
     test("Click with contents - fires trashcanOpen", function() {
@@ -94,9 +94,9 @@ suite("Trashcan", function() {
 
       assertEventFired(
           this.eventsFireStub, Blockly.Events.TrashcanOpen,
-          {isOpen: true}, this.workspace.id);
+          {isOpen: true, type: eventUtils.TRASHCAN_OPEN}, this.workspace.id);
       assertEventNotFired(
-          this.eventsFireStub, Blockly.Events.Click, {});
+          this.eventsFireStub, Blockly.Events.Click, {type: eventUtils.TRASHCAN_OPEN});
     });
     test("Click outside trashcan - fires trashcanClose", function() {
       sinon.stub(this.trashcan.flyout, 'isVisible').returns(true);
@@ -109,9 +109,9 @@ suite("Trashcan", function() {
 
       assertEventFired(
           this.eventsFireStub, Blockly.Events.TrashcanOpen,
-          {isOpen: false}, this.workspace.id);
+          {isOpen: false, type: eventUtils.TRASHCAN_OPEN}, this.workspace.id);
       assertEventFired(
-          this.eventsFireStub, Blockly.Events.Click, {targetType: 'workspace'},
+          this.eventsFireStub, Blockly.Events.Click, {targetType: 'workspace', type: eventUtils.CLICK},
           this.workspace.id, null);
     });
   });
diff --git a/tests/mocha/workspace_svg_test.js b/tests/mocha/workspace_svg_test.js
index c6af088ec..6271b2795 100644
--- a/tests/mocha/workspace_svg_test.js
+++ b/tests/mocha/workspace_svg_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.workspaceSvg');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, assertEventNotFired, assertVariableValues, createFireChangeListenerSpy, defineStackBlock, sharedTestSetup, sharedTestTeardown, workspaceTeardown} = goog.require('Blockly.test.helpers');
 const {testAWorkspace} = goog.require('Blockly.test.workspaceHelpers');
 
@@ -182,6 +183,7 @@ suite('WorkspaceSvg', function() {
         oldScale: 1,
         viewTop: metrics.viewTop,
         viewLeft: metrics.viewLeft,
+        type: eventUtils.VIEWPORT_CHANGE,
       };
       assertSpyFiredViewportEvent(
           eventsFireStub, workspace, expectedProperties);
@@ -294,9 +296,10 @@ suite('WorkspaceSvg', function() {
             '<block type="controls_if" x="188" y="163"></block>'), this.workspace);
         this.clock.runAll();
         assertEventNotFired(
-            this.eventsFireStub, Blockly.Events.ViewportChange, {});
+            this.eventsFireStub, Blockly.Events.ViewportChange, {type: eventUtils.VIEWPORT_CHANGE});
         assertEventNotFired(
-            this.changeListenerSpy, Blockly.Events.ViewportChange, {});
+            this.changeListenerSpy, Blockly.Events.ViewportChange,
+            {type: eventUtils.VIEWPORT_CHANGE});
       });
       test('domToWorkspace at 0,0 that doesn\'t trigger scroll', function() {
         // 4 blocks with space in center.
@@ -317,9 +320,11 @@ suite('WorkspaceSvg', function() {
         Blockly.Xml.domToWorkspace(xmlDom, this.workspace);
         this.clock.runAll();
         assertEventNotFired(
-            this.eventsFireStub, Blockly.Events.ViewportChange, {});
+            this.eventsFireStub, Blockly.Events.ViewportChange,
+            {type: eventUtils.VIEWPORT_CHANGE});
         assertEventNotFired(
-            this.changeListenerSpy, Blockly.Events.ViewportChange, {});
+            this.changeListenerSpy, Blockly.Events.ViewportChange,
+            {type: eventUtils.VIEWPORT_CHANGE});
       });
       test.skip('domToWorkspace multiple blocks triggers one viewport event', function() {
         // TODO: Un-skip after adding filtering for consecutive viewport events.
diff --git a/tests/mocha/zoom_controls_test.js b/tests/mocha/zoom_controls_test.js
index e17bccddb..3d9d1f2d4 100644
--- a/tests/mocha/zoom_controls_test.js
+++ b/tests/mocha/zoom_controls_test.js
@@ -6,6 +6,7 @@
 
 goog.module('Blockly.test.zoomControls');
 
+const eventUtils = goog.require('Blockly.Events.utils');
 const {assertEventFired, assertEventNotFired, sharedTestSetup, sharedTestTeardown, simulateClick} = goog.require('Blockly.test.helpers');
 
 
@@ -31,10 +32,10 @@ suite("Zoom Controls", function() {
 
       assertEventFired(
           this.eventsFireStub, Blockly.Events.Click,
-          {targetType: 'zoom_controls'}, this.workspace.id, null);
+          {targetType: 'zoom_controls', type: eventUtils.CLICK}, this.workspace.id, null);
       assertEventNotFired(
           this.eventsFireStub, Blockly.Events.Click,
-          {targetType: 'workspace'});
+          {targetType: 'workspace', type: eventUtils.CLICK});
       chai.assert.closeTo(this.workspace.getScale(), 1.2, 0.05);
     });
     test("Zoom out", function() {
@@ -42,10 +43,10 @@ suite("Zoom Controls", function() {
 
       assertEventFired(
           this.eventsFireStub, Blockly.Events.Click,
-          {targetType: 'zoom_controls'}, this.workspace.id, null);
+          {targetType: 'zoom_controls', type: eventUtils.CLICK}, this.workspace.id, null);
       assertEventNotFired(
           this.eventsFireStub, Blockly.Events.Click,
-          {targetType: 'workspace'});
+          {targetType: 'workspace', type: eventUtils.CLICK});
       chai.assert.closeTo(this.workspace.getScale(), 0.8, 0.05);
     });
     test("Reset zoom", function() {
@@ -53,10 +54,10 @@ suite("Zoom Controls", function() {
 
       assertEventFired(
           this.eventsFireStub, Blockly.Events.Click,
-          {targetType: 'zoom_controls'}, this.workspace.id, null);
+          {targetType: 'zoom_controls', type: eventUtils.CLICK}, this.workspace.id, null);
       assertEventNotFired(
           this.eventsFireStub, Blockly.Events.Click,
-          {targetType: 'workspace'});
+          {targetType: 'workspace', type: eventUtils.CLICK});
       chai.assert.equal(this.workspace.getScale(), 1);
     });
   });