diff --git a/core/block.js b/core/block.js
index 6a20efaf9..b33fe7bb4 100644
--- a/core/block.js
+++ b/core/block.js
@@ -84,7 +84,8 @@ Blockly.Block = function(workspace, prototypeName, opt_id) {
    */
   this.childBlocks_ = [];
 
-  /** @type {boolean}
+  /**
+   * @type {boolean}
    * @private
    */
   this.deletable_ = true;
@@ -222,13 +223,13 @@ Blockly.Block.prototype.dispose = function(healStack) {
   }
   // Then dispose of myself.
   // Dispose of all inputs and their fields.
-  for (var j = 0, input; input = this.inputList[j]; j++) {
+  for (var i = 0, input; input = this.inputList[i]; i++) {
     input.dispose();
   }
   this.inputList.length = 0;
   // Dispose of any remaining connections (next/previous/output).
   var connections = this.getConnections_(true);
-  for (i = 0; i < connections.length; i++) {
+  for (var i = 0; i < connections.length; i++) {
     var connection = connections[i];
     if (connection.isConnected()) {
       connection.disconnect();
@@ -586,7 +587,7 @@ Blockly.Block.prototype.setConnectionsHidden = function(hidden) {
     for (var i = 0, connection; connection = myConnections[i]; i++) {
       connection.setHidden(hidden);
       if (connection.isSuperior()) {
-        child = connection.targetBlock();
+        var child = connection.targetBlock();
         if (child) {
           child.setConnectionsHidden(hidden);
         }
@@ -843,7 +844,7 @@ Blockly.Block.prototype.getInputsInline = function() {
       return false;
     }
   }
-  for (i = 1; i < this.inputList.length; i++) {
+  for (var i = 1; i < this.inputList.length; i++) {
     if (this.inputList[i - 1].type == Blockly.INPUT_VALUE &&
         this.inputList[i].type == Blockly.DUMMY_INPUT) {
       // Dummy input after a value input.  Inline them.
@@ -1063,7 +1064,7 @@ Blockly.Block.prototype.interpolate_ = function(message, args, lastDummyAlign) {
   };
   // Populate block with inputs and fields.
   var fieldStack = [];
-  for (i = 0; i < elements.length; i++) {
+  for (var i = 0; i < elements.length; i++) {
     var element = elements[i];
     if (typeof element == 'string') {
       fieldStack.push([element, undefined]);
diff --git a/core/block_svg.js b/core/block_svg.js
index f0fea7f56..7bdccb58e 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -119,7 +119,7 @@ Blockly.BlockSvg.prototype.initSvg = function() {
     input.init();
   }
   var icons = this.getIcons();
-  for (i = 0; i < icons.length; i++) {
+  for (var i = 0; i < icons.length; i++) {
     icons[i].createIcon();
   }
   this.updateColour();
@@ -447,7 +447,7 @@ Blockly.BlockSvg.prototype.setCollapsed = function(collapsed) {
   var COLLAPSED_INPUT_NAME = '_TEMP_COLLAPSED_INPUT';
   if (collapsed) {
     var icons = this.getIcons();
-    for (i = 0; i < icons.length; i++) {
+    for (var i = 0; i < icons.length; i++) {
       icons[i].setVisible(false);
     }
     var text = this.toString(Blockly.COLLAPSE_CHARS);
@@ -464,7 +464,7 @@ Blockly.BlockSvg.prototype.setCollapsed = function(collapsed) {
     renderList[0] = this;
   }
   if (this.rendered) {
-    for (var j = 0, block; block = renderList[j]; j++) {
+    for (var i = 0, block; block = renderList[i]; i++) {
       block.render();
     }
     // Don't bump neighbours.
@@ -497,7 +497,7 @@ Blockly.BlockSvg.prototype.tab = function(start, forward) {
       }
     }
   }
-  i = list.indexOf(start);
+  var i = list.indexOf(start);
   if (i == -1) {
     // No start location, start at the beginning or end.
     i = forward ? -1 : list.length;
@@ -792,12 +792,12 @@ Blockly.BlockSvg.prototype.moveConnections_ = function(dx, dy) {
     myConnections[i].moveBy(dx, dy);
   }
   var icons = this.getIcons();
-  for (i = 0; i < icons.length; i++) {
+  for (var i = 0; i < icons.length; i++) {
     icons[i].computeIconLocation();
   }
 
   // Recurse through all blocks attached under this one.
-  for (i = 0; i < this.childBlocks_.length; i++) {
+  for (var i = 0; i < this.childBlocks_.length; i++) {
     this.childBlocks_[i].moveConnections_(dx, dy);
   }
 };
@@ -862,7 +862,7 @@ Blockly.BlockSvg.prototype.onMouseMove_ = function(e) {
   if (Blockly.dragMode_ == Blockly.DRAG_FREE) {
     // Unrestricted dragging.
     var dxy = goog.math.Coordinate.difference(oldXY, this.dragStartXY_);
-    group = this.getSvgRoot();
+    var group = this.getSvgRoot();
     group.translate_ = 'translate(' + newXY.x + ',' + newXY.y + ')';
     group.setAttribute('transform', group.translate_ + group.skew_);
     // Drag all the nested bubbles.
@@ -878,7 +878,7 @@ Blockly.BlockSvg.prototype.onMouseMove_ = function(e) {
     var closestConnection = null;
     var localConnection = null;
     var radiusConnection = Blockly.SNAP_RADIUS;
-    for (i = 0; i < myConnections.length; i++) {
+    for (var i = 0; i < myConnections.length; i++) {
       var myConnection = myConnections[i];
       var neighbour = myConnection.closest(radiusConnection, dxy);
       if (neighbour.connection) {
diff --git a/core/blockly.js b/core/blockly.js
index 2f2d196b7..0536332d8 100644
--- a/core/blockly.js
+++ b/core/blockly.js
@@ -462,10 +462,10 @@ Blockly.getMainWorkspaceMetrics_ = function() {
     var bottomEdge = Math.max(contentY + contentHeight + viewHeight / 2,
                               contentY + viewHeight);
   } else {
-    leftEdge = blockBox.x;
-    rightEdge = leftEdge + blockBox.width;
-    topEdge = blockBox.y;
-    bottomEdge = topEdge + blockBox.height;
+    var leftEdge = blockBox.x;
+    var rightEdge = leftEdge + blockBox.width;
+    var topEdge = blockBox.y;
+    var bottomEdge = topEdge + blockBox.height;
   }
   var absoluteLeft = 0;
   if (!this.RTL && this.toolbox_) {
diff --git a/core/events.js b/core/events.js
index cd6880dd8..bc4299e55 100644
--- a/core/events.js
+++ b/core/events.js
@@ -161,7 +161,7 @@ Blockly.Events.filter = function(queueIn, forward) {
     }
   }
   // Remove null events.
-  for (i = queue.length - 1; i >= 0; i--) {
+  for (var i = queue.length - 1; i >= 0; i--) {
     if (queue[i].isNull()) {
       queue.splice(i, 1);
     }
@@ -172,7 +172,7 @@ Blockly.Events.filter = function(queueIn, forward) {
   }
   // Move mutation events to the top of the queue.
   // Intentionally skip first event.
-  for (var k = 1, event; event = queue[k]; k++) {
+  for (var i = 1, event; event = queue[i]; i++) {
     if (event.type == Blockly.Events.CHANGE &&
         event.element == 'mutation') {
       queue.unshift(queue.splice(i, 1)[0]);
@@ -254,7 +254,7 @@ Blockly.Events.getDescendantIds_ = function(block) {
  * Decode the JSON into an event.
  * @param {!Object} json JSON representation.
  * @param {!Blockly.Workspace} workspace Target workspace for event.
- * @return {!Blockly.Events.Abstract} the event represented by the json.
+ * @return {!Blockly.Events.Abstract} The event represented by the JSON.
  */
 Blockly.Events.fromJson = function(json, workspace) {
   var event;
diff --git a/core/field.js b/core/field.js
index 302ffb996..305ecd6d6 100644
--- a/core/field.js
+++ b/core/field.js
@@ -254,11 +254,11 @@ Blockly.Field.prototype.render_ = function() {
       var width = Blockly.Field.cacheWidths_[key];
     } else {
       try {
-        width = this.textElement_.getComputedTextLength();
+        var width = this.textElement_.getComputedTextLength();
       } catch (e) {
         // MSIE 11 is known to throw "Unexpected call to method or property
         // access." if Blockly is hidden.
-        width = this.textElement_.textContent.length * 8;
+        var width = this.textElement_.textContent.length * 8;
       }
       if (Blockly.Field.cacheWidths_) {
         Blockly.Field.cacheWidths_[key] = width;
@@ -269,7 +269,7 @@ Blockly.Field.prototype.render_ = function() {
           width + Blockly.BlockSvg.SEP_SPACE_X);
     }
   } else {
-    width = 0;
+    var width = 0;
   }
   this.size_.width = width;
 };
diff --git a/core/field_angle.js b/core/field_angle.js
index 5eb49a2dd..b5ca196ce 100644
--- a/core/field_angle.js
+++ b/core/field_angle.js
@@ -66,7 +66,7 @@ Blockly.FieldAngle.prototype.setValidator = function(handler) {
         if (v1 === undefined) {
           v1 = value;
         }
-        v2 = Blockly.FieldAngle.angleValidator.call(this, v1);
+        var v2 = Blockly.FieldAngle.angleValidator.call(this, v1);
         if (v2 === undefined) {
           v2 = v1;
         }
diff --git a/core/field_variable.js b/core/field_variable.js
index 421f9ea08..8e5bac966 100644
--- a/core/field_variable.js
+++ b/core/field_variable.js
@@ -64,7 +64,7 @@ Blockly.FieldVariable.prototype.setValidator = function(handler) {
         if (v1 === undefined) {
           v1 = value;
         }
-        v2 = Blockly.FieldVariable.dropdownChange.call(this, v1);
+        var v2 = Blockly.FieldVariable.dropdownChange.call(this, v1);
         if (v2 === undefined) {
           v2 = v1;
         }
@@ -128,7 +128,7 @@ Blockly.FieldVariable.dropdownCreate = function() {
     var variableList =
         Blockly.Variables.allVariables(this.sourceBlock_.workspace);
   } else {
-    variableList = [];
+    var variableList = [];
   }
   // Ensure that the currently selected variable is an option.
   var name = this.getText();
diff --git a/core/inject.js b/core/inject.js
index fb3cd82d8..4f84b24a3 100644
--- a/core/inject.js
+++ b/core/inject.js
@@ -211,26 +211,27 @@ Blockly.createMainWorkspace_ = function(svg, options) {
             var blockXY = block.getRelativeToSurfaceXY();
             var blockHW = block.getHeightWidth();
             // Bump any block that's above the top back inside.
-            var overflow = edgeTop + MARGIN - blockHW.height - blockXY.y;
-            if (overflow > 0) {
-              block.moveBy(0, overflow);
+            var overflowTop = edgeTop + MARGIN - blockHW.height - blockXY.y;
+            if (overflowTop > 0) {
+              block.moveBy(0, overflowTop);
             }
             // Bump any block that's below the bottom back inside.
-            overflow = edgeTop + metrics.viewHeight - MARGIN - blockXY.y;
-            if (overflow < 0) {
-              block.moveBy(0, overflow);
+            var overflowBottom =
+                edgeTop + metrics.viewHeight - MARGIN - blockXY.y;
+            if (overflowBottom < 0) {
+              block.moveBy(0, overflowBottom);
             }
             // Bump any block that's off the left back inside.
-            overflow = MARGIN + edgeLeft -
+            var overflowLeft = MARGIN + edgeLeft -
                 blockXY.x - (options.RTL ? 0 : blockHW.width);
-            if (overflow > 0) {
-              block.moveBy(overflow, 0);
+            if (overflowLeft > 0) {
+              block.moveBy(overflowLeft, 0);
             }
             // Bump any block that's off the right back inside.
-            overflow = edgeLeft + metrics.viewWidth - MARGIN -
+            var overflowRight = edgeLeft + metrics.viewWidth - MARGIN -
                 blockXY.x + (options.RTL ? blockHW.width : 0);
-            if (overflow < 0) {
-              block.moveBy(overflow, 0);
+            if (overflowRight < 0) {
+              block.moveBy(overflowRight, 0);
             }
           }
         }
diff --git a/core/mutator.js b/core/mutator.js
index 50586e082..a53babfd9 100644
--- a/core/mutator.js
+++ b/core/mutator.js
@@ -115,7 +115,7 @@ Blockly.Mutator.prototype.createEditor_ = function() {
       quarkXml.appendChild(goog.dom.createDom('block', {'type': quarkName}));
     }
   } else {
-    quarkXml = null;
+    var quarkXml = null;
   }
   var workspaceOptions = {
     languageTree: quarkXml,
@@ -223,8 +223,8 @@ Blockly.Mutator.prototype.setVisible = function(visible) {
       var margin = this.workspace_.flyout_.CORNER_RADIUS * 2;
       var x = this.workspace_.flyout_.width_ + margin;
     } else {
-      margin = 16;
-      x = margin;
+      var margin = 16;
+      var x = margin;
     }
     if (this.block_.RTL) {
       x = -x;
@@ -283,7 +283,7 @@ Blockly.Mutator.prototype.workspaceChanged_ = function() {
   // When the mutator's workspace changes, update the source block.
   if (this.rootBlock_.workspace == this.workspace_) {
     Blockly.Events.setGroup(true);
-    block = this.block_;
+    var block = this.block_;
     var oldMutationDom = block.mutationToDom();
     var oldMutation = oldMutationDom && Blockly.Xml.domToText(oldMutationDom);
     // Switch off rendering while the source block is rebuilt.
diff --git a/core/options.js b/core/options.js
index 41e4edc3f..57ff21f0a 100644
--- a/core/options.js
+++ b/core/options.js
@@ -45,26 +45,26 @@ Blockly.Options = function(options) {
     var hasDisable = false;
     var hasSounds = false;
   } else {
-    languageTree = Blockly.Options.parseToolboxTree(options['toolbox']);
-    hasCategories = Boolean(languageTree &&
+    var languageTree = Blockly.Options.parseToolboxTree(options['toolbox']);
+    var hasCategories = Boolean(languageTree &&
         languageTree.getElementsByTagName('category').length);
-    hasTrashcan = options['trashcan'];
+    var hasTrashcan = options['trashcan'];
     if (hasTrashcan === undefined) {
       hasTrashcan = hasCategories;
     }
-    hasCollapse = options['collapse'];
+    var hasCollapse = options['collapse'];
     if (hasCollapse === undefined) {
       hasCollapse = hasCategories;
     }
-    hasComments = options['comments'];
+    var hasComments = options['comments'];
     if (hasComments === undefined) {
       hasComments = hasCategories;
     }
-    hasDisable = options['disable'];
+    var hasDisable = options['disable'];
     if (hasDisable === undefined) {
       hasDisable = hasCategories;
     }
-    hasSounds = options['sounds'];
+    var hasSounds = options['sounds'];
     if (hasSounds === undefined) {
       hasSounds = true;
     }
diff --git a/core/toolbox.js b/core/toolbox.js
index 32a10f177..2d765da6e 100644
--- a/core/toolbox.js
+++ b/core/toolbox.js
@@ -285,7 +285,7 @@ Blockly.Toolbox.prototype.addColour_ = function(opt_tree) {
       if (this.hasColours_) {
         var border = '8px solid ' + (child.hexColour || '#ddd');
       } else {
-        border = 'none';
+        var border = 'none';
       }
       if (this.workspace_.RTL) {
         element.style.borderRight = border;
@@ -321,7 +321,7 @@ Blockly.Toolbox.prototype.getClientRect = function() {
     return new goog.math.Rect(toolboxRect.left, -BIG_NUM, width, BIG_NUM * 2);
   }
   // LTR
-  width = BIG_NUM + toolboxRect.width + toolboxRect.left;
+  var width = BIG_NUM + toolboxRect.width + toolboxRect.left;
   return new goog.math.Rect(-BIG_NUM, -BIG_NUM, width, BIG_NUM * 2);
 };
 
diff --git a/core/tooltip.js b/core/tooltip.js
index 86da01d65..6e520e65b 100644
--- a/core/tooltip.js
+++ b/core/tooltip.js
@@ -317,7 +317,7 @@ Blockly.Tooltip.wrap_ = function(text, limit) {
     // Seed the list with evenly spaced linebreaks.
     var steps = words.length / lineCount;
     var insertedBreaks = 1;
-    for (i = 0; i < words.length - 1; i++) {
+    for (var i = 0; i < words.length - 1; i++) {
       if (insertedBreaks < (i + 1.5) / steps) {
         insertedBreaks++;
         wordBreaks[i] = true;
@@ -358,7 +358,7 @@ Blockly.Tooltip.wrapScore_ = function(words, wordBreaks, limit) {
   var maxLength = Math.max.apply(Math, lineLengths);
 
   var score = 0;
-  for (i = 0; i < lineLengths.length; i++) {
+  for (var i = 0; i < lineLengths.length; i++) {
     // Optimize for width.
     // -2 points per char over limit (scaled to the power of 1.5).
     score -= Math.pow(Math.abs(limit - lineLengths[i]), 1.5) * 2;
diff --git a/core/trashcan.js b/core/trashcan.js
index a192deb81..429d613c6 100644
--- a/core/trashcan.js
+++ b/core/trashcan.js
@@ -167,7 +167,7 @@ Blockly.Trashcan.prototype.createDom = function() {
   body.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href',
       this.workspace_.options.pathToMedia + Blockly.SPRITE.url);
 
-  clip = Blockly.createSvgElement('clipPath',
+  var clip = Blockly.createSvgElement('clipPath',
       {'id': 'blocklyTrashLidClipPath' + rnd},
       this.svgGroup_);
   Blockly.createSvgElement('rect',
diff --git a/core/utils.js b/core/utils.js
index a53256867..08961e235 100644
--- a/core/utils.js
+++ b/core/utils.js
@@ -104,7 +104,7 @@ Blockly.bindEvent_ = function(node, name, thisObject, func) {
       func.call(thisObject, e);
     };
   } else {
-    wrapFunc = func;
+    var wrapFunc = func;
   }
   node.addEventListener(name, wrapFunc, false);
   var bindData = [[node, name, wrapFunc]];
@@ -374,8 +374,8 @@ Blockly.commonWordPrefix = function(array, opt_shortest) {
       wordPrefix = len + 1;
     }
   }
-  for (i = 1; i < array.length; i++) {
-    letter = array[i][len];
+  for (var i = 1; i < array.length; i++) {
+    var letter = array[i][len];
     if (letter && letter != ' ') {
       return wordPrefix;
     }
@@ -409,8 +409,8 @@ Blockly.commonWordSuffix = function(array, opt_shortest) {
       wordPrefix = len + 1;
     }
   }
-  for (i = 1; i < array.length; i++) {
-    letter = array[i].charAt(array[i].length - len - 1);
+  for (var i = 1; i < array.length; i++) {
+    var letter = array[i].charAt(array[i].length - len - 1);
     if (letter && letter != ' ') {
       return wordPrefix;
     }
@@ -478,7 +478,7 @@ Blockly.tokenizeInterpolation = function(message) {
       }
     }
   }
-  text = buffer.join('');
+  var text = buffer.join('');
   if (text) {
     tokens.push(text);
   }
diff --git a/core/variables.js b/core/variables.js
index e4048a995..12b8eeb06 100644
--- a/core/variables.js
+++ b/core/variables.js
@@ -123,12 +123,12 @@ Blockly.Variables.flyoutCategory = function(workspace) {
       // <block type="variables_get" gap="24">
       //   <field name="VAR">item</field>
       // </block>
-      block = goog.dom.createDom('block');
+      var block = goog.dom.createDom('block');
       block.setAttribute('type', 'variables_get');
       if (Blockly.Blocks['variables_set']) {
         block.setAttribute('gap', 24);
       }
-      field = goog.dom.createDom('field', null, variableList[i]);
+      var field = goog.dom.createDom('field', null, variableList[i]);
       field.setAttribute('name', 'VAR');
       block.appendChild(field);
       xmlList.push(block);
diff --git a/core/workspace.js b/core/workspace.js
index 66a49ea99..e67fbe564 100644
--- a/core/workspace.js
+++ b/core/workspace.js
@@ -235,7 +235,7 @@ Blockly.Workspace.prototype.undo = function(redo) {
   }
   events = Blockly.Events.filter(events, redo);
   Blockly.Events.recordUndo = false;
-  for (i = 0; event = events[i]; i++) {
+  for (var i = 0, event; event = events[i]; i++) {
     event.run(redo);
   }
   Blockly.Events.recordUndo = true;
diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index 12e52cba3..3c62acac1 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -486,7 +486,7 @@ Blockly.WorkspaceSvg.prototype.paste = function(xmlBlock) {
       if (!collide) {
         // Check for blocks in snap range to any of its connections.
         var connections = block.getConnections_(false);
-        for (var j = 0, connection; connection = connections[j]; j++) {
+        for (var i = 0, connection; connection = connections[i]; i++) {
           var neighbour = connection.closest(Blockly.SNAP_RADIUS,
               new goog.math.Coordinate(blockX, blockY));
           if (neighbour.connection) {
@@ -808,7 +808,7 @@ Blockly.WorkspaceSvg.prototype.showContextMenu_ = function(e) {
       }
     }
   }
-  for (i = 0; i < topBlocks.length; i++) {
+  for (var i = 0; i < topBlocks.length; i++) {
     addDeletableBlocks(topBlocks[i]);
   }
   var deleteOption = {
diff --git a/core/xml.js b/core/xml.js
index 5f4d9a987..e2651e025 100644
--- a/core/xml.js
+++ b/core/xml.js
@@ -109,7 +109,7 @@ Blockly.Xml.blockToDom = function(block) {
     element.appendChild(dataElement);
   }
 
-  for (i = 0; input = block.inputList[i]; i++) {
+  for (var i = 0, input; input = block.inputList[i]; i++) {
     var container;
     var empty = true;
     if (input.type == Blockly.DUMMY_INPUT) {
@@ -156,11 +156,11 @@ Blockly.Xml.blockToDom = function(block) {
 
   var nextBlock = block.getNextBlock();
   if (nextBlock) {
-    container = goog.dom.createDom('next', null,
+    var container = goog.dom.createDom('next', null,
         Blockly.Xml.blockToDom(nextBlock));
     element.appendChild(container);
   }
-  shadow = block.nextConnection && block.nextConnection.getShadowDom();
+  var shadow = block.nextConnection && block.nextConnection.getShadowDom();
   if (shadow && (!nextBlock || !nextBlock.isShadow())) {
     container.appendChild(Blockly.Xml.cloneShadow_(shadow));
   }
@@ -337,7 +337,7 @@ Blockly.Xml.domToBlock = function(xmlBlock, workspace) {
     for (var i = blocks.length - 1; i >= 0; i--) {
       blocks[i].initSvg();
     }
-    for (i = blocks.length - 1; i >= 0; i--) {
+    for (var i = blocks.length - 1; i >= 0; i--) {
       blocks[i].render(false);
     }
     // Populating the connection database may be defered until after the blocks
diff --git a/core/zoom_controls.js b/core/zoom_controls.js
index 31f06fa9b..d50110829 100644
--- a/core/zoom_controls.js
+++ b/core/zoom_controls.js
@@ -131,7 +131,7 @@ Blockly.ZoomControls.prototype.createDom = function() {
   zoomoutSvg.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href',
       workspace.options.pathToMedia + Blockly.SPRITE.url);
 
-  clip = Blockly.createSvgElement('clipPath',
+  var clip = Blockly.createSvgElement('clipPath',
       {'id': 'blocklyZoominClipPath' + rnd},
       this.svgGroup_);
   Blockly.createSvgElement('rect',
@@ -147,7 +147,7 @@ Blockly.ZoomControls.prototype.createDom = function() {
   zoominSvg.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href',
       workspace.options.pathToMedia + Blockly.SPRITE.url);
 
-  clip = Blockly.createSvgElement('clipPath',
+  var clip = Blockly.createSvgElement('clipPath',
       {'id': 'blocklyZoomresetClipPath' + rnd},
       this.svgGroup_);
   Blockly.createSvgElement('rect',