chore: replace more uses of var with const and let (#5628)

* chore: fix uses of var in core/block_dragger

* chore: fix uses of var in core/extensions.js

* chore: fix uses of var in core/field_multilineinput.js

* chore: fix uses of var in assorted core files

* chore: fix uses of var in node test runner and playground screenshot code

* fix: undefined return from measureFontMetrics

* fix: violations of no-const-assign

* chore: only one variable declaration per line

core/block_dragger.js

@@ -275,12 +275,16 @@ BlockDragger.prototype.endDrag = function(e, currentDragDeltaXY) {
 
   const preventMove = !!this.dragTarget_ &&
       this.dragTarget_.shouldPreventMove(this.draggingBlock_);
+  /** @type {Coordinate} */
+  let newLoc;
+  /** @type {Coordinate} */
+  let delta;
   if (preventMove) {
-    var newLoc = this.startXY_;
+    newLoc = this.startXY_;
   } else {
     const newValues = this.getNewLocationAfterDrag_(currentDragDeltaXY);
-    var delta = newValues.delta;
-    var newLoc = newValues.newLocation;
+    delta = newValues.delta;
+    newLoc = newValues.newLocation;
   }
   this.draggingBlock_.moveOffDragSurface(newLoc);
 

core/extensions.js

@@ -95,7 +95,7 @@ const registerMutator = function(name, mixinObj, opt_helperFn, opt_blockList) {
   const errorPrefix = 'Error when registering mutator "' + name + '": ';
 
   checkHasMutatorProperties(errorPrefix, mixinObj);
-  var hasMutatorDialog = checkMutatorDialog(mixinObj, errorPrefix);
+  const hasMutatorDialog = checkMutatorDialog(mixinObj, errorPrefix);
 
   if (opt_helperFn && (typeof opt_helperFn !== 'function')) {
     throw Error(errorPrefix + 'Extension "' + name + '" is not a function');
@@ -261,8 +261,8 @@ const checkMutatorDialog = function(object, errorPrefix) {
  *     not actually a function.
  */
 const checkHasFunctionPair = function(object, name1, name2, errorPrefix) {
-  var has1 = object[name1] !== undefined;
-  var has2 = object[name2] !== undefined;
+  const has1 = object[name1] !== undefined;
+  const has2 = object[name2] !== undefined;
 
   if (has1 && has2) {
     if (typeof object[name1] !== 'function') {
@@ -285,8 +285,8 @@ const checkHasFunctionPair = function(object, name1, name2, errorPrefix) {
  * @param {!Object} object The object to inspect.
  */
 const checkHasMutatorProperties = function(errorPrefix, object) {
-  var hasXmlHooks = checkXmlHooks(object, errorPrefix);
-  var hasJsonHooks = checkJsonHooks(object, errorPrefix);
+  const hasXmlHooks = checkXmlHooks(object, errorPrefix);
+  const hasJsonHooks = checkJsonHooks(object, errorPrefix);
   if (!hasXmlHooks && !hasJsonHooks) {
     throw Error(
         errorPrefix +

core/field_multilineinput.js

@@ -246,7 +246,7 @@ FieldMultilineInput.prototype.render_ = function() {
   }
 
   if (this.isBeingEdited_) {
-    var htmlInput = /** @type {!HTMLElement} */ (this.htmlInput_);
+    const htmlInput = /** @type {!HTMLElement} */ (this.htmlInput_);
     if (this.isOverflowedY_) {
       dom.addClass(htmlInput, 'blocklyHtmlTextAreaInputOverflowedY');
     } else {
@@ -265,7 +265,7 @@ FieldMultilineInput.prototype.render_ = function() {
     } else {
       this.resizeEditor_();
     }
-    var htmlInput = /** @type {!HTMLElement} */ (this.htmlInput_);
+    const htmlInput = /** @type {!HTMLElement} */ (this.htmlInput_);
     if (!this.isTextValid_) {
       dom.addClass(htmlInput, 'blocklyInvalidInput');
       aria.setState(htmlInput, aria.State.INVALID, true);
@@ -284,7 +284,7 @@ FieldMultilineInput.prototype.updateSize_ = function() {
   const nodes = this.textGroup_.childNodes;
   let totalWidth = 0;
   let totalHeight = 0;
-  for (var i = 0; i < nodes.length; i++) {
+  for (let i = 0; i < nodes.length; i++) {
     const tspan = /** @type {!Element} */ (nodes[i]);
     const textWidth = dom.getTextWidth(tspan);
     if (textWidth > totalWidth) {
@@ -306,7 +306,7 @@ FieldMultilineInput.prototype.updateSize_ = function() {
     const fontWeight = this.getConstants().FIELD_TEXT_FONTWEIGHT;
     const fontFamily = this.getConstants().FIELD_TEXT_FONTFAMILY;
 
-    for (var i = 0; i < actualEditorLines.length; i++) {
+    for (let i = 0; i < actualEditorLines.length; i++) {
       if (actualEditorLines[i].length > this.maxDisplayLength) {
         actualEditorLines[i] =
             actualEditorLines[i].substring(0, this.maxDisplayLength);

core/keyboard_nav/ast_node.js

@@ -432,7 +432,7 @@ ASTNode.prototype.findPrevForField_ = function() {
  * @private
  */
 ASTNode.prototype.navigateBetweenStacks_ = function(forward) {
-  var curLocation = this.getLocation();
+  let curLocation = this.getLocation();
   if (curLocation.getSourceBlock) {
     curLocation = /** @type {!IASTNodeLocationWithBlock} */ (curLocation)
                       .getSourceBlock();

core/serialization/blocks.js

@@ -45,7 +45,7 @@ const {inputTypes} = goog.require('Blockly.inputTypes');
  * }}
  * @alias Blockly.serialization.blocks.ConnectionState
  */
-var ConnectionState;
+let ConnectionState;
 exports.ConnectionState = ConnectionState;
 
 /**
@@ -67,7 +67,7 @@ exports.ConnectionState = ConnectionState;
  * }}
  * @alias Blockly.serialization.blocks.State
  */
-var State;
+let State;
 exports.State = State;
 
 /**

core/serialization/variables.js

@@ -35,7 +35,7 @@ const {Workspace} = goog.requireType('Blockly.Workspace');
  * }}
  * @alias Blockly.serialization.variables.State
  */
-var State;
+let State;
 exports.State = State;
 
 /**

core/trashcan.js

@@ -722,7 +722,7 @@ Trashcan.prototype.cleanBlockJson_ = function(json) {
     }
 
     const inputs = json['inputs'];
-    for (var name in inputs) {
+    for (const name in inputs) {
       const input = inputs[name];
       cleanRec(input['block']);
       cleanRec(input['shadow']);

core/utils/dom.js

@@ -413,8 +413,11 @@ const measureFontMetrics = function(text, fontSize, fontWeight, fontFamily) {
   div.appendChild(block);
 
   document.body.appendChild(div);
+  const result = {
+    height: 0,
+    baseline: 0,
+  };
   try {
-    var result = {};
     div.style.alignItems = 'baseline';
     result.baseline = block.offsetTop - span.offsetTop;
     div.style.alignItems = 'flex-end';

core/workspace_svg.js

@@ -2688,8 +2688,8 @@ WorkspaceSvg.prototype.hideChaff = function(opt_onlyClosePopups) {
   WidgetDiv.hide();
   DropDownDiv.hideWithoutAnimation();
 
-  var onlyClosePopups = !!opt_onlyClosePopups;
-  var autoHideables = this.getComponentManager().getComponents(
+  const onlyClosePopups = !!opt_onlyClosePopups;
+  const autoHideables = this.getComponentManager().getComponents(
       ComponentManager.Capability.AUTOHIDEABLE, true);
   autoHideables.forEach(
       (autoHideable) => autoHideable.autoHide(onlyClosePopups));