diff --git a/src/addons/ReactComponentWithPureRenderMixin.js b/src/addons/ReactComponentWithPureRenderMixin.js
index 87cfd2b2c0..d057ac71a4 100644
--- a/src/addons/ReactComponentWithPureRenderMixin.js
+++ b/src/addons/ReactComponentWithPureRenderMixin.js
@@ -9,7 +9,7 @@
 * @providesModule ReactComponentWithPureRenderMixin
 */
 
-"use strict";
+'use strict';
 
 var shallowEqual = require('shallowEqual');
 
diff --git a/src/addons/ReactRAFBatchingStrategy.js b/src/addons/ReactRAFBatchingStrategy.js
index a95dcab4d1..1d3df579a7 100644
--- a/src/addons/ReactRAFBatchingStrategy.js
+++ b/src/addons/ReactRAFBatchingStrategy.js
@@ -10,7 +10,9 @@
  * @typechecks static-only
  */
 
-"use strict";
+/* global requestAnimationFrame:true */
+
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 var ReactUpdates = require('ReactUpdates');
diff --git a/src/addons/__tests__/update-test.js b/src/addons/__tests__/update-test.js
index 3c5dda7752..be2cb3a0e6 100644
--- a/src/addons/__tests__/update-test.js
+++ b/src/addons/__tests__/update-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var update = require('update');
 
diff --git a/src/addons/link/LinkedStateMixin.js b/src/addons/link/LinkedStateMixin.js
index 2afcd512fe..350bfa594b 100644
--- a/src/addons/link/LinkedStateMixin.js
+++ b/src/addons/link/LinkedStateMixin.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ReactLink = require('ReactLink');
 var ReactStateSetters = require('ReactStateSetters');
diff --git a/src/addons/link/ReactLink.js b/src/addons/link/ReactLink.js
index 4ca505126b..8d803c7ffd 100644
--- a/src/addons/link/ReactLink.js
+++ b/src/addons/link/ReactLink.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * ReactLink encapsulates a common pattern in which a component wants to modify
diff --git a/src/addons/link/__tests__/LinkedStateMixin-test.js b/src/addons/link/__tests__/LinkedStateMixin-test.js
index 524ba41a8b..3a4bee13d7 100644
--- a/src/addons/link/__tests__/LinkedStateMixin-test.js
+++ b/src/addons/link/__tests__/LinkedStateMixin-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 /*jshint evil:true */
 
diff --git a/src/addons/link/__tests__/ReactLinkPropTypes-test.js b/src/addons/link/__tests__/ReactLinkPropTypes-test.js
index b5f55b42e3..76dadd39e8 100644
--- a/src/addons/link/__tests__/ReactLinkPropTypes-test.js
+++ b/src/addons/link/__tests__/ReactLinkPropTypes-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var emptyFunction = require('emptyFunction');
 var LinkPropTypes = require('ReactLink').PropTypes;
@@ -40,7 +40,7 @@ function typeCheckPass(declaration, value) {
     'testComponent',
     ReactPropTypeLocations.prop
   );
-  expect(error).toBe(undefined);
+  expect(error).toBe(null);
 }
 
 describe('ReactLink', function() {
diff --git a/src/addons/transitions/ReactCSSTransitionGroup.js b/src/addons/transitions/ReactCSSTransitionGroup.js
index dd481eef6b..ea45de4e4c 100644
--- a/src/addons/transitions/ReactCSSTransitionGroup.js
+++ b/src/addons/transitions/ReactCSSTransitionGroup.js
@@ -10,7 +10,7 @@
  * @providesModule ReactCSSTransitionGroup
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 
diff --git a/src/addons/transitions/ReactCSSTransitionGroupChild.js b/src/addons/transitions/ReactCSSTransitionGroupChild.js
index 6bdcf90e16..e85ee2c585 100644
--- a/src/addons/transitions/ReactCSSTransitionGroupChild.js
+++ b/src/addons/transitions/ReactCSSTransitionGroupChild.js
@@ -10,7 +10,7 @@
  * @providesModule ReactCSSTransitionGroupChild
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 
@@ -64,7 +64,9 @@ var ReactCSSTransitionGroupChild = React.createClass({
 
       // Usually this optional callback is used for informing an owner of
       // a leave animation and telling it to remove the child.
-      finishCallback && finishCallback();
+      if (finishCallback) {
+        finishCallback();
+      }
     };
 
     ReactTransitionEvents.addEndEventListener(node, endListener);
diff --git a/src/addons/transitions/ReactTransitionChildMapping.js b/src/addons/transitions/ReactTransitionChildMapping.js
index 63fd96527e..1621fb1e7b 100644
--- a/src/addons/transitions/ReactTransitionChildMapping.js
+++ b/src/addons/transitions/ReactTransitionChildMapping.js
@@ -10,7 +10,7 @@
  * @providesModule ReactTransitionChildMapping
  */
 
-"use strict";
+'use strict';
 
 var ReactChildren = require('ReactChildren');
 
diff --git a/src/addons/transitions/ReactTransitionEvents.js b/src/addons/transitions/ReactTransitionEvents.js
index 9dd32ca3e3..cdf8abfc88 100644
--- a/src/addons/transitions/ReactTransitionEvents.js
+++ b/src/addons/transitions/ReactTransitionEvents.js
@@ -9,7 +9,7 @@
  * @providesModule ReactTransitionEvents
  */
 
-"use strict";
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
diff --git a/src/addons/transitions/ReactTransitionGroup.js b/src/addons/transitions/ReactTransitionGroup.js
index 80296e4e48..7fe408ce7c 100644
--- a/src/addons/transitions/ReactTransitionGroup.js
+++ b/src/addons/transitions/ReactTransitionGroup.js
@@ -9,7 +9,7 @@
  * @providesModule ReactTransitionGroup
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactTransitionChildMapping = require('ReactTransitionChildMapping');
diff --git a/src/addons/transitions/__tests__/ReactCSSTransitionGroup-test.js b/src/addons/transitions/__tests__/ReactCSSTransitionGroup-test.js
index 67c7be0b49..dabd3c5819 100644
--- a/src/addons/transitions/__tests__/ReactCSSTransitionGroup-test.js
+++ b/src/addons/transitions/__tests__/ReactCSSTransitionGroup-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactCSSTransitionGroup;
diff --git a/src/addons/transitions/__tests__/ReactTransitionChildMapping-test.js b/src/addons/transitions/__tests__/ReactTransitionChildMapping-test.js
index 1e7653508d..bc701cb9a3 100644
--- a/src/addons/transitions/__tests__/ReactTransitionChildMapping-test.js
+++ b/src/addons/transitions/__tests__/ReactTransitionChildMapping-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTransitionChildMapping;
diff --git a/src/addons/transitions/__tests__/ReactTransitionGroup-test.js b/src/addons/transitions/__tests__/ReactTransitionGroup-test.js
index 1a4b23fc25..0f50c160d2 100644
--- a/src/addons/transitions/__tests__/ReactTransitionGroup-test.js
+++ b/src/addons/transitions/__tests__/ReactTransitionGroup-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTransitionGroup;
diff --git a/src/addons/update.js b/src/addons/update.js
index 34e078b20e..dd03d714d4 100644
--- a/src/addons/update.js
+++ b/src/addons/update.js
@@ -9,7 +9,7 @@
  * @providesModule update
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 var keyOf = require('keyOf');
diff --git a/src/browser/ClientReactRootIndex.js b/src/browser/ClientReactRootIndex.js
index 2a4633b031..0db7f33b69 100644
--- a/src/browser/ClientReactRootIndex.js
+++ b/src/browser/ClientReactRootIndex.js
@@ -10,7 +10,7 @@
  * @typechecks
  */
 
-"use strict";
+'use strict';
 
 var nextReactRootIndex = 0;
 
diff --git a/src/browser/ReactBrowserEventEmitter.js b/src/browser/ReactBrowserEventEmitter.js
index f2c4a5dd78..a3fa84f73e 100644
--- a/src/browser/ReactBrowserEventEmitter.js
+++ b/src/browser/ReactBrowserEventEmitter.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginHub = require('EventPluginHub');
@@ -126,7 +126,7 @@ var topEventMapping = {
 /**
  * To ensure no conflicts with other potential React instances on the page
  */
-var topListenersIDKey = "_reactListenersID" + String(Math.random()).slice(2);
+var topListenersIDKey = '_reactListenersID' + String(Math.random()).slice(2);
 
 function getListeningForDocument(mountAt) {
   // In IE8, `mountAt` is a host object and doesn't have `hasOwnProperty`
diff --git a/src/browser/ReactDOM.js b/src/browser/ReactDOM.js
index d4b1303b44..c3e77d040c 100644
--- a/src/browser/ReactDOM.js
+++ b/src/browser/ReactDOM.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactElementValidator = require('ReactElementValidator');
diff --git a/src/browser/ReactPutListenerQueue.js b/src/browser/ReactPutListenerQueue.js
index e47b6edcfe..50361fdc1d 100644
--- a/src/browser/ReactPutListenerQueue.js
+++ b/src/browser/ReactPutListenerQueue.js
@@ -9,7 +9,7 @@
  * @providesModule ReactPutListenerQueue
  */
 
-"use strict";
+'use strict';
 
 var PooledClass = require('PooledClass');
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
diff --git a/src/browser/ReactReconcileTransaction.js b/src/browser/ReactReconcileTransaction.js
index 008890a256..257493e9da 100644
--- a/src/browser/ReactReconcileTransaction.js
+++ b/src/browser/ReactReconcileTransaction.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var CallbackQueue = require('CallbackQueue');
 var PooledClass = require('PooledClass');
diff --git a/src/browser/ReactWithAddons.js b/src/browser/ReactWithAddons.js
index 25d98f8b45..cb0b5931ba 100644
--- a/src/browser/ReactWithAddons.js
+++ b/src/browser/ReactWithAddons.js
@@ -16,7 +16,7 @@
  * place to live inside React core.
  */
 
-"use strict";
+'use strict';
 
 var LinkedStateMixin = require('LinkedStateMixin');
 var React = require('React');
diff --git a/src/browser/__tests__/ReactBrowserEventEmitter-test.js b/src/browser/__tests__/ReactBrowserEventEmitter-test.js
index 39b6feb627..b70fd61e81 100644
--- a/src/browser/__tests__/ReactBrowserEventEmitter-test.js
+++ b/src/browser/__tests__/ReactBrowserEventEmitter-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules')
     .dontMock('EventPluginHub')
diff --git a/src/browser/__tests__/ReactDOM-test.js b/src/browser/__tests__/ReactDOM-test.js
index 24fd941f67..71649cb931 100644
--- a/src/browser/__tests__/ReactDOM-test.js
+++ b/src/browser/__tests__/ReactDOM-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactTestUtils = require('ReactTestUtils');
diff --git a/src/browser/__tests__/ReactWebWorker-test.js b/src/browser/__tests__/ReactWebWorker-test.js
index 5acdcbc928..9f7c9bc543 100644
--- a/src/browser/__tests__/ReactWebWorker-test.js
+++ b/src/browser/__tests__/ReactWebWorker-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 describe('ReactWebWorker', function() {
   ;(typeof Worker == 'undefined' ? xit : it)('can run React in a web worker', function() {
diff --git a/src/browser/__tests__/findDOMNode-test.js b/src/browser/__tests__/findDOMNode-test.js
index 7cb2f4fd8f..464c67df06 100644
--- a/src/browser/__tests__/findDOMNode-test.js
+++ b/src/browser/__tests__/findDOMNode-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactTestUtils = require('ReactTestUtils');
@@ -48,4 +48,3 @@ describe('findDOMNode', function() {
   });
 
 });
-
diff --git a/src/browser/eventPlugins/AnalyticsEventPluginFactory.js b/src/browser/eventPlugins/AnalyticsEventPluginFactory.js
index e4ec0fe55e..858e3d5525 100644
--- a/src/browser/eventPlugins/AnalyticsEventPluginFactory.js
+++ b/src/browser/eventPlugins/AnalyticsEventPluginFactory.js
@@ -74,7 +74,7 @@
  * usage.
  */
 
-"use strict";
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
@@ -152,7 +152,7 @@ function extractEvents(
     return null;
   }
 
-  var analyticsEventsArr = analyticsEventsStr.split(",");
+  var analyticsEventsArr = analyticsEventsStr.split(',');
   if (!analyticsData.hasOwnProperty(analyticsID)) {
     initAnalyticsDataForID(analyticsID, analyticsEventsArr);
   }
diff --git a/src/browser/eventPlugins/BeforeInputEventPlugin.js b/src/browser/eventPlugins/BeforeInputEventPlugin.js
index 449aa5cf48..0441c57d0e 100644
--- a/src/browser/eventPlugins/BeforeInputEventPlugin.js
+++ b/src/browser/eventPlugins/BeforeInputEventPlugin.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPropagators = require('EventPropagators');
@@ -256,7 +256,7 @@ function extractCompositionEvent(
   }
 
   if (!eventType) {
-    return;
+    return null;
   }
 
   if (useFallbackCompositionData) {
@@ -427,7 +427,7 @@ function extractBeforeInputEvent(
   // If no characters are being inserted, no BeforeInput event should
   // be fired.
   if (!chars) {
-    return;
+    return null;
   }
 
   var event = SyntheticInputEvent.getPooled(
@@ -490,7 +490,7 @@ var BeforeInputEventPlugin = {
         topLevelTarget,
         topLevelTargetID,
         nativeEvent
-      ),
+      )
     ];
   }
 };
diff --git a/src/browser/eventPlugins/ChangeEventPlugin.js b/src/browser/eventPlugins/ChangeEventPlugin.js
index cc2243a359..92271602d1 100644
--- a/src/browser/eventPlugins/ChangeEventPlugin.js
+++ b/src/browser/eventPlugins/ChangeEventPlugin.js
@@ -9,7 +9,7 @@
  * @providesModule ChangeEventPlugin
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginHub = require('EventPluginHub');
diff --git a/src/browser/eventPlugins/DefaultEventPluginOrder.js b/src/browser/eventPlugins/DefaultEventPluginOrder.js
index f61748ef26..e0f5b16316 100644
--- a/src/browser/eventPlugins/DefaultEventPluginOrder.js
+++ b/src/browser/eventPlugins/DefaultEventPluginOrder.js
@@ -9,7 +9,7 @@
  * @providesModule DefaultEventPluginOrder
  */
 
-"use strict";
+'use strict';
 
  var keyOf = require('keyOf');
 
diff --git a/src/browser/eventPlugins/EnterLeaveEventPlugin.js b/src/browser/eventPlugins/EnterLeaveEventPlugin.js
index bef0d4221b..1ec6d02b09 100644
--- a/src/browser/eventPlugins/EnterLeaveEventPlugin.js
+++ b/src/browser/eventPlugins/EnterLeaveEventPlugin.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPropagators = require('EventPropagators');
diff --git a/src/browser/eventPlugins/FallbackCompositionState.js b/src/browser/eventPlugins/FallbackCompositionState.js
index f557aef465..44ea12b3d2 100644
--- a/src/browser/eventPlugins/FallbackCompositionState.js
+++ b/src/browser/eventPlugins/FallbackCompositionState.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var PooledClass = require('PooledClass');
 
@@ -58,19 +58,21 @@ assign(FallbackCompositionState.prototype, {
       return this._fallbackText;
     }
 
-    var endValue = this.getText();
+    var start;
     var startValue = this._startText;
     var startLength = startValue.length;
+    var end;
+    var endValue = this.getText();
     var endLength = endValue.length;
 
-    for (var start = 0; start < startLength; start++) {
+    for (start = 0; start < startLength; start++) {
       if (startValue[start] !== endValue[start]) {
         break;
       }
     }
 
     var minEnd = startLength - start;
-    for (var end = 1; end <= minEnd; end++) {
+    for (end = 1; end <= minEnd; end++) {
       if (startValue[startLength - end] !== endValue[endLength - end]) {
         break;
       }
diff --git a/src/browser/eventPlugins/MobileSafariClickEventPlugin.js b/src/browser/eventPlugins/MobileSafariClickEventPlugin.js
index 9d695167db..774860a4fd 100644
--- a/src/browser/eventPlugins/MobileSafariClickEventPlugin.js
+++ b/src/browser/eventPlugins/MobileSafariClickEventPlugin.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 
diff --git a/src/browser/eventPlugins/ResponderEventPlugin.js b/src/browser/eventPlugins/ResponderEventPlugin.js
index 44d322af7d..dde77d6cf6 100644
--- a/src/browser/eventPlugins/ResponderEventPlugin.js
+++ b/src/browser/eventPlugins/ResponderEventPlugin.js
@@ -9,7 +9,7 @@
  * @providesModule ResponderEventPlugin
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginUtils = require('EventPluginUtils');
diff --git a/src/browser/eventPlugins/SelectEventPlugin.js b/src/browser/eventPlugins/SelectEventPlugin.js
index 7fa54c0602..7a93798c42 100644
--- a/src/browser/eventPlugins/SelectEventPlugin.js
+++ b/src/browser/eventPlugins/SelectEventPlugin.js
@@ -9,7 +9,7 @@
  * @providesModule SelectEventPlugin
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPropagators = require('EventPropagators');
@@ -94,8 +94,8 @@ function constructSelectEvent(nativeEvent) {
   // won't dispatch.
   if (mouseDown ||
       activeElement == null ||
-      activeElement != getActiveElement()) {
-    return;
+      activeElement !== getActiveElement()) {
+    return null;
   }
 
   // Only fire when selection has actually changed.
diff --git a/src/browser/eventPlugins/SimpleEventPlugin.js b/src/browser/eventPlugins/SimpleEventPlugin.js
index f3d5743fcf..d0d2d23a9f 100644
--- a/src/browser/eventPlugins/SimpleEventPlugin.js
+++ b/src/browser/eventPlugins/SimpleEventPlugin.js
@@ -9,7 +9,7 @@
  * @providesModule SimpleEventPlugin
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginUtils = require('EventPluginUtils');
diff --git a/src/browser/eventPlugins/TapEventPlugin.js b/src/browser/eventPlugins/TapEventPlugin.js
index 788b3513aa..fe43085f2d 100644
--- a/src/browser/eventPlugins/TapEventPlugin.js
+++ b/src/browser/eventPlugins/TapEventPlugin.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginUtils = require('EventPluginUtils');
@@ -117,7 +117,7 @@ var TapEventPlugin = {
       usedTouchTime = Date.now();
     } else {
       if (usedTouch && (Date.now() - usedTouchTime < TOUCH_DELAY)) {
-        return;
+        return null;
       }
     }
     var event = null;
diff --git a/src/browser/eventPlugins/__tests__/AnalyticsEventPlugin-test.js b/src/browser/eventPlugins/__tests__/AnalyticsEventPlugin-test.js
index cc5f9902ef..ff717f3973 100644
--- a/src/browser/eventPlugins/__tests__/AnalyticsEventPlugin-test.js
+++ b/src/browser/eventPlugins/__tests__/AnalyticsEventPlugin-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 
diff --git a/src/browser/eventPlugins/__tests__/EnterLeaveEventPlugin-test.js b/src/browser/eventPlugins/__tests__/EnterLeaveEventPlugin-test.js
index 365a5965c8..721ea4bd1e 100644
--- a/src/browser/eventPlugins/__tests__/EnterLeaveEventPlugin-test.js
+++ b/src/browser/eventPlugins/__tests__/EnterLeaveEventPlugin-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var EnterLeaveEventPlugin;
 var EventConstants;
diff --git a/src/browser/eventPlugins/__tests__/FallbackCompositionState-test.js b/src/browser/eventPlugins/__tests__/FallbackCompositionState-test.js
index 893e8ef858..935debaa30 100644
--- a/src/browser/eventPlugins/__tests__/FallbackCompositionState-test.js
+++ b/src/browser/eventPlugins/__tests__/FallbackCompositionState-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('FallbackCompositionState', function() {
   var FallbackCompositionState;
diff --git a/src/browser/eventPlugins/__tests__/ResponderEventPlugin-test.js b/src/browser/eventPlugins/__tests__/ResponderEventPlugin-test.js
index d480efcbe1..e849779fdf 100644
--- a/src/browser/eventPlugins/__tests__/ResponderEventPlugin-test.js
+++ b/src/browser/eventPlugins/__tests__/ResponderEventPlugin-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var EventPluginHub;
 var EventConstants;
diff --git a/src/browser/findDOMNode.js b/src/browser/findDOMNode.js
index 32f7c46f6d..501bb3f82a 100644
--- a/src/browser/findDOMNode.js
+++ b/src/browser/findDOMNode.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 var ReactInstanceMap = require('ReactInstanceMap');
 var ReactMount = require('ReactMount');
 
@@ -35,9 +35,9 @@ function findDOMNode(componentOrElement) {
   }
   invariant(
     componentOrElement.render == null ||
-    typeof(componentOrElement.render) !== 'function',
-    'Component (with keys: %s) contains `render` method '
-    +'but is not mounted in the DOM',
+    typeof componentOrElement.render !== 'function',
+    'Component (with keys: %s) contains `render` method ' +
+    'but is not mounted in the DOM',
     Object.keys(componentOrElement)
   );
   invariant(
diff --git a/src/browser/server/ReactMarkupChecksum.js b/src/browser/server/ReactMarkupChecksum.js
index 1cfb1e97d3..d3b248a4ce 100644
--- a/src/browser/server/ReactMarkupChecksum.js
+++ b/src/browser/server/ReactMarkupChecksum.js
@@ -9,7 +9,7 @@
  * @providesModule ReactMarkupChecksum
  */
 
-"use strict";
+'use strict';
 
 var adler32 = require('adler32');
 
diff --git a/src/browser/server/ReactServerRendering.js b/src/browser/server/ReactServerRendering.js
index 670d752412..c5e291e9e6 100644
--- a/src/browser/server/ReactServerRendering.js
+++ b/src/browser/server/ReactServerRendering.js
@@ -9,7 +9,7 @@
  * @typechecks static-only
  * @providesModule ReactServerRendering
  */
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactInstanceHandles = require('ReactInstanceHandles');
@@ -38,7 +38,8 @@ function renderToString(element) {
 
     return transaction.perform(function() {
       var componentInstance = instantiateReactComponent(element, null);
-      var markup = componentInstance.mountComponent(id, transaction, emptyObject);
+      var markup =
+        componentInstance.mountComponent(id, transaction, emptyObject);
       return ReactMarkupChecksum.addChecksumToMarkup(markup);
     }, null);
   } finally {
diff --git a/src/browser/server/ReactServerRenderingTransaction.js b/src/browser/server/ReactServerRenderingTransaction.js
index 7833b58831..e9fea07b04 100644
--- a/src/browser/server/ReactServerRenderingTransaction.js
+++ b/src/browser/server/ReactServerRenderingTransaction.js
@@ -10,7 +10,7 @@
  * @typechecks
  */
 
-"use strict";
+'use strict';
 
 var PooledClass = require('PooledClass');
 var CallbackQueue = require('CallbackQueue');
diff --git a/src/browser/server/ServerReactRootIndex.js b/src/browser/server/ServerReactRootIndex.js
index 1329fe7485..b8b6f98fab 100644
--- a/src/browser/server/ServerReactRootIndex.js
+++ b/src/browser/server/ServerReactRootIndex.js
@@ -10,7 +10,7 @@
  * @typechecks
  */
 
-"use strict";
+'use strict';
 
 /**
  * Size of the reactRoot ID space. We generate random numbers for React root
diff --git a/src/browser/server/__tests__/ReactServerRendering-test.js b/src/browser/server/__tests__/ReactServerRendering-test.js
index d6b9a5c593..cee8ba19e8 100644
--- a/src/browser/server/__tests__/ReactServerRendering-test.js
+++ b/src/browser/server/__tests__/ReactServerRendering-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 require('mock-modules')
   .dontMock('ExecutionEnvironment')
diff --git a/src/browser/syntheticEvents/SyntheticClipboardEvent.js b/src/browser/syntheticEvents/SyntheticClipboardEvent.js
index 167ff4e495..2f459413a9 100644
--- a/src/browser/syntheticEvents/SyntheticClipboardEvent.js
+++ b/src/browser/syntheticEvents/SyntheticClipboardEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticEvent = require('SyntheticEvent');
 
@@ -41,4 +41,3 @@ function SyntheticClipboardEvent(dispatchConfig, dispatchMarker, nativeEvent) {
 SyntheticEvent.augmentClass(SyntheticClipboardEvent, ClipboardEventInterface);
 
 module.exports = SyntheticClipboardEvent;
-
diff --git a/src/browser/syntheticEvents/SyntheticCompositionEvent.js b/src/browser/syntheticEvents/SyntheticCompositionEvent.js
index cde736b247..0636f6e981 100644
--- a/src/browser/syntheticEvents/SyntheticCompositionEvent.js
+++ b/src/browser/syntheticEvents/SyntheticCompositionEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticEvent = require('SyntheticEvent');
 
@@ -41,4 +41,3 @@ SyntheticEvent.augmentClass(
 );
 
 module.exports = SyntheticCompositionEvent;
-
diff --git a/src/browser/syntheticEvents/SyntheticDragEvent.js b/src/browser/syntheticEvents/SyntheticDragEvent.js
index 7568327294..9234591c58 100644
--- a/src/browser/syntheticEvents/SyntheticDragEvent.js
+++ b/src/browser/syntheticEvents/SyntheticDragEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticMouseEvent = require('SyntheticMouseEvent');
 
diff --git a/src/browser/syntheticEvents/SyntheticEvent.js b/src/browser/syntheticEvents/SyntheticEvent.js
index 2d17e6cf9d..dd8b3dcd3c 100644
--- a/src/browser/syntheticEvents/SyntheticEvent.js
+++ b/src/browser/syntheticEvents/SyntheticEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var PooledClass = require('PooledClass');
 
@@ -88,13 +88,21 @@ assign(SyntheticEvent.prototype, {
   preventDefault: function() {
     this.defaultPrevented = true;
     var event = this.nativeEvent;
-    event.preventDefault ? event.preventDefault() : event.returnValue = false;
+    if (event.preventDefault) {
+      event.preventDefault();
+    } else {
+      event.returnValue = false;
+    }
     this.isDefaultPrevented = emptyFunction.thatReturnsTrue;
   },
 
   stopPropagation: function() {
     var event = this.nativeEvent;
-    event.stopPropagation ? event.stopPropagation() : event.cancelBubble = true;
+    if (event.stopPropagation) {
+      event.stopPropagation();
+    } else {
+      event.cancelBubble = true;
+    }
     this.isPropagationStopped = emptyFunction.thatReturnsTrue;
   },
 
diff --git a/src/browser/syntheticEvents/SyntheticFocusEvent.js b/src/browser/syntheticEvents/SyntheticFocusEvent.js
index ea96a02c0a..d8e9b3fd8e 100644
--- a/src/browser/syntheticEvents/SyntheticFocusEvent.js
+++ b/src/browser/syntheticEvents/SyntheticFocusEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticUIEvent = require('SyntheticUIEvent');
 
diff --git a/src/browser/syntheticEvents/SyntheticInputEvent.js b/src/browser/syntheticEvents/SyntheticInputEvent.js
index e0153139b2..8aeb37c199 100644
--- a/src/browser/syntheticEvents/SyntheticInputEvent.js
+++ b/src/browser/syntheticEvents/SyntheticInputEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticEvent = require('SyntheticEvent');
 
@@ -42,4 +42,3 @@ SyntheticEvent.augmentClass(
 );
 
 module.exports = SyntheticInputEvent;
-
diff --git a/src/browser/syntheticEvents/SyntheticKeyboardEvent.js b/src/browser/syntheticEvents/SyntheticKeyboardEvent.js
index 4969a20f5c..fec450021d 100644
--- a/src/browser/syntheticEvents/SyntheticKeyboardEvent.js
+++ b/src/browser/syntheticEvents/SyntheticKeyboardEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticUIEvent = require('SyntheticUIEvent');
 
diff --git a/src/browser/syntheticEvents/SyntheticMouseEvent.js b/src/browser/syntheticEvents/SyntheticMouseEvent.js
index 67ee558e96..86cfd17914 100644
--- a/src/browser/syntheticEvents/SyntheticMouseEvent.js
+++ b/src/browser/syntheticEvents/SyntheticMouseEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticUIEvent = require('SyntheticUIEvent');
 var ViewportMetrics = require('ViewportMetrics');
diff --git a/src/browser/syntheticEvents/SyntheticTouchEvent.js b/src/browser/syntheticEvents/SyntheticTouchEvent.js
index 8f48a5cb9a..f645945b0a 100644
--- a/src/browser/syntheticEvents/SyntheticTouchEvent.js
+++ b/src/browser/syntheticEvents/SyntheticTouchEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticUIEvent = require('SyntheticUIEvent');
 
diff --git a/src/browser/syntheticEvents/SyntheticUIEvent.js b/src/browser/syntheticEvents/SyntheticUIEvent.js
index 1966070722..bcbcd55b5f 100644
--- a/src/browser/syntheticEvents/SyntheticUIEvent.js
+++ b/src/browser/syntheticEvents/SyntheticUIEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticEvent = require('SyntheticEvent');
 
diff --git a/src/browser/syntheticEvents/SyntheticWheelEvent.js b/src/browser/syntheticEvents/SyntheticWheelEvent.js
index 49c874b163..d89be0a5c9 100644
--- a/src/browser/syntheticEvents/SyntheticWheelEvent.js
+++ b/src/browser/syntheticEvents/SyntheticWheelEvent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var SyntheticMouseEvent = require('SyntheticMouseEvent');
 
diff --git a/src/browser/syntheticEvents/__tests__/SyntheticEvent-test.js b/src/browser/syntheticEvents/__tests__/SyntheticEvent-test.js
index 0b95a5abe5..545dea44b5 100644
--- a/src/browser/syntheticEvents/__tests__/SyntheticEvent-test.js
+++ b/src/browser/syntheticEvents/__tests__/SyntheticEvent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var SyntheticEvent;
 
diff --git a/src/browser/syntheticEvents/__tests__/SyntheticWheelEvent-test.js b/src/browser/syntheticEvents/__tests__/SyntheticWheelEvent-test.js
index b7a97b6baa..9a871da175 100644
--- a/src/browser/syntheticEvents/__tests__/SyntheticWheelEvent-test.js
+++ b/src/browser/syntheticEvents/__tests__/SyntheticWheelEvent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var SyntheticWheelEvent;
 
diff --git a/src/browser/ui/React.js b/src/browser/ui/React.js
index 5cbc45fa96..977d4689df 100644
--- a/src/browser/ui/React.js
+++ b/src/browser/ui/React.js
@@ -11,7 +11,7 @@
 
 /* globals __REACT_DEVTOOLS_GLOBAL_HOOK__*/
 
-"use strict";
+'use strict';
 
 var DOMPropertyOperations = require('DOMPropertyOperations');
 var EventPluginUtils = require('EventPluginUtils');
diff --git a/src/browser/ui/ReactBrowserComponentMixin.js b/src/browser/ui/ReactBrowserComponentMixin.js
index ba3dc2a4f3..eaed83f5d2 100644
--- a/src/browser/ui/ReactBrowserComponentMixin.js
+++ b/src/browser/ui/ReactBrowserComponentMixin.js
@@ -9,7 +9,7 @@
  * @providesModule ReactBrowserComponentMixin
  */
 
-"use strict";
+'use strict';
 
 var findDOMNode = require('findDOMNode');
 
diff --git a/src/browser/ui/ReactComponentBrowserEnvironment.js b/src/browser/ui/ReactComponentBrowserEnvironment.js
index e5b3bbd116..ee9e540f5f 100644
--- a/src/browser/ui/ReactComponentBrowserEnvironment.js
+++ b/src/browser/ui/ReactComponentBrowserEnvironment.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var ReactDOMIDOperations = require('ReactDOMIDOperations');
 var ReactMount = require('ReactMount');
diff --git a/src/browser/ui/ReactDOMComponent.js b/src/browser/ui/ReactDOMComponent.js
index 3d7031f13b..033aa977bc 100644
--- a/src/browser/ui/ReactDOMComponent.js
+++ b/src/browser/ui/ReactDOMComponent.js
@@ -10,7 +10,9 @@
  * @typechecks static-only
  */
 
-"use strict";
+/* global hasOwnProperty:true */
+
+'use strict';
 
 var CSSPropertyOperations = require('CSSPropertyOperations');
 var DOMProperty = require('DOMProperty');
@@ -73,9 +75,9 @@ function assertValidProps(props) {
     if (props.contentEditable && props.children != null) {
       console.warn(
         'A component is `contentEditable` and contains `children` managed by ' +
-        'React. It is now your responsibility to guarantee that none of those '+
-        'nodes are unexpectedly modified or duplicated. This is probably not ' +
-        'intentional.'
+        'React. It is now your responsibility to guarantee that none of ' +
+        'those nodes are unexpectedly modified or duplicated. This is ' +
+        'probably not intentional.'
       );
     }
   }
diff --git a/src/browser/ui/ReactDOMIDOperations.js b/src/browser/ui/ReactDOMIDOperations.js
index 6705433e48..1586ac880d 100644
--- a/src/browser/ui/ReactDOMIDOperations.js
+++ b/src/browser/ui/ReactDOMIDOperations.js
@@ -12,7 +12,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var CSSPropertyOperations = require('CSSPropertyOperations');
 var DOMChildrenOperations = require('DOMChildrenOperations');
diff --git a/src/browser/ui/ReactDOMSelection.js b/src/browser/ui/ReactDOMSelection.js
index 1ad780676c..bdc7b3f0bc 100644
--- a/src/browser/ui/ReactDOMSelection.js
+++ b/src/browser/ui/ReactDOMSelection.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMSelection
  */
 
-"use strict";
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
diff --git a/src/browser/ui/ReactDOMTextComponent.js b/src/browser/ui/ReactDOMTextComponent.js
index 4999d750db..3e15a7863b 100644
--- a/src/browser/ui/ReactDOMTextComponent.js
+++ b/src/browser/ui/ReactDOMTextComponent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var DOMPropertyOperations = require('DOMPropertyOperations');
 var ReactComponentBrowserEnvironment =
diff --git a/src/browser/ui/ReactDefaultInjection.js b/src/browser/ui/ReactDefaultInjection.js
index fcc9e6ba8a..3e2d21d618 100644
--- a/src/browser/ui/ReactDefaultInjection.js
+++ b/src/browser/ui/ReactDefaultInjection.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDefaultInjection
  */
 
-"use strict";
+'use strict';
 
 var BeforeInputEventPlugin = require('BeforeInputEventPlugin');
 var ChangeEventPlugin = require('ChangeEventPlugin');
diff --git a/src/browser/ui/ReactEventListener.js b/src/browser/ui/ReactEventListener.js
index e51fcd9c62..41835ba928 100644
--- a/src/browser/ui/ReactEventListener.js
+++ b/src/browser/ui/ReactEventListener.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var EventListener = require('EventListener');
 var ExecutionEnvironment = require('ExecutionEnvironment');
@@ -123,7 +123,7 @@ var ReactEventListener = {
   trapBubbledEvent: function(topLevelType, handlerBaseName, handle) {
     var element = handle;
     if (!element) {
-      return;
+      return null;
     }
     return EventListener.listen(
       element,
@@ -145,7 +145,7 @@ var ReactEventListener = {
   trapCapturedEvent: function(topLevelType, handlerBaseName, handle) {
     var element = handle;
     if (!element) {
-      return;
+      return null;
     }
     return EventListener.capture(
       element,
diff --git a/src/browser/ui/ReactInjection.js b/src/browser/ui/ReactInjection.js
index bea0124f4a..b959a6fdb1 100644
--- a/src/browser/ui/ReactInjection.js
+++ b/src/browser/ui/ReactInjection.js
@@ -9,7 +9,7 @@
  * @providesModule ReactInjection
  */
 
-"use strict";
+'use strict';
 
 var DOMProperty = require('DOMProperty');
 var EventPluginHub = require('EventPluginHub');
diff --git a/src/browser/ui/ReactInputSelection.js b/src/browser/ui/ReactInputSelection.js
index 023090f8f8..6ae32bed3c 100644
--- a/src/browser/ui/ReactInputSelection.js
+++ b/src/browser/ui/ReactInputSelection.js
@@ -9,7 +9,7 @@
  * @providesModule ReactInputSelection
  */
 
-"use strict";
+'use strict';
 
 var ReactDOMSelection = require('ReactDOMSelection');
 
diff --git a/src/browser/ui/ReactMount.js b/src/browser/ui/ReactMount.js
index 4d51f02f65..816441faae 100644
--- a/src/browser/ui/ReactMount.js
+++ b/src/browser/ui/ReactMount.js
@@ -9,7 +9,7 @@
  * @providesModule ReactMount
  */
 
-"use strict";
+'use strict';
 
 var DOMProperty = require('DOMProperty');
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
@@ -435,7 +435,9 @@ var ReactMount = {
       container,
       shouldReuseMarkup
     ).getPublicInstance();
-    callback && callback.call(component);
+    if (callback) {
+      callback.call(component);
+    }
     return component;
   },
 
diff --git a/src/browser/ui/__tests__/ReactDOMComponent-test.js b/src/browser/ui/__tests__/ReactDOMComponent-test.js
index b69773cd24..f66efa2877 100644
--- a/src/browser/ui/__tests__/ReactDOMComponent-test.js
+++ b/src/browser/ui/__tests__/ReactDOMComponent-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 var mocks = require('mocks');
diff --git a/src/browser/ui/__tests__/ReactDOMIDOperations-test.js b/src/browser/ui/__tests__/ReactDOMIDOperations-test.js
index 47cafa9794..06bc85b021 100644
--- a/src/browser/ui/__tests__/ReactDOMIDOperations-test.js
+++ b/src/browser/ui/__tests__/ReactDOMIDOperations-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 describe('ReactDOMIDOperations', function() {
   var DOMPropertyOperations = require('DOMPropertyOperations');
diff --git a/src/browser/ui/__tests__/ReactDOMTextComponent-test.js b/src/browser/ui/__tests__/ReactDOMTextComponent-test.js
index 37a1b9822b..f8716fbdc1 100644
--- a/src/browser/ui/__tests__/ReactDOMTextComponent-test.js
+++ b/src/browser/ui/__tests__/ReactDOMTextComponent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 
diff --git a/src/browser/ui/__tests__/ReactMount-test.js b/src/browser/ui/__tests__/ReactMount-test.js
index f9d3aad8d2..8634524178 100644
--- a/src/browser/ui/__tests__/ReactMount-test.js
+++ b/src/browser/ui/__tests__/ReactMount-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 
diff --git a/src/browser/ui/__tests__/ReactMountDestruction-test.js b/src/browser/ui/__tests__/ReactMountDestruction-test.js
index 35cb05be85..a49c88da51 100644
--- a/src/browser/ui/__tests__/ReactMountDestruction-test.js
+++ b/src/browser/ui/__tests__/ReactMountDestruction-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 
diff --git a/src/browser/ui/__tests__/ReactRenderDocument-test.js b/src/browser/ui/__tests__/ReactRenderDocument-test.js
index 2a9d9f3bed..97e5971a67 100644
--- a/src/browser/ui/__tests__/ReactRenderDocument-test.js
+++ b/src/browser/ui/__tests__/ReactRenderDocument-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactInstanceMap;
diff --git a/src/browser/ui/dom/CSSProperty.js b/src/browser/ui/dom/CSSProperty.js
index b93c093ed1..0b924974e8 100644
--- a/src/browser/ui/dom/CSSProperty.js
+++ b/src/browser/ui/dom/CSSProperty.js
@@ -9,7 +9,7 @@
  * @providesModule CSSProperty
  */
 
-"use strict";
+'use strict';
 
 /**
  * CSS properties which accept numbers but are not in units of "px".
diff --git a/src/browser/ui/dom/CSSPropertyOperations.js b/src/browser/ui/dom/CSSPropertyOperations.js
index 22f2ae0bee..f40ce5f213 100644
--- a/src/browser/ui/dom/CSSPropertyOperations.js
+++ b/src/browser/ui/dom/CSSPropertyOperations.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var CSSProperty = require('CSSProperty');
 var ExecutionEnvironment = require('ExecutionEnvironment');
diff --git a/src/browser/ui/dom/DOMChildrenOperations.js b/src/browser/ui/dom/DOMChildrenOperations.js
index 0a566e5c00..27aa8c2438 100644
--- a/src/browser/ui/dom/DOMChildrenOperations.js
+++ b/src/browser/ui/dom/DOMChildrenOperations.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var Danger = require('Danger');
 var ReactMultiChildUpdateTypes = require('ReactMultiChildUpdateTypes');
@@ -100,7 +100,8 @@ var DOMChildrenOperations = {
     // List of children that will be moved or removed.
     var updatedChildren = null;
 
-    for (var i = 0; update = updates[i]; i++) {
+    for (var i = 0; i < updates.length; i++) {
+      update = updates[i];
       if (update.type === ReactMultiChildUpdateTypes.MOVE_EXISTING ||
           update.type === ReactMultiChildUpdateTypes.REMOVE_NODE) {
         var updatedIndex = update.fromIndex;
@@ -112,7 +113,7 @@ var DOMChildrenOperations = {
           'processUpdates(): Unable to find child %s of element. This ' +
           'probably means the DOM was unexpectedly mutated (e.g., by the ' +
           'browser), usually due to forgetting a <tbody> when using tables, ' +
-          'nesting tags like <form>, <p>, or <a>, or using non-SVG elements '+
+          'nesting tags like <form>, <p>, or <a>, or using non-SVG elements ' +
           'in an <svg> parent. Try inspecting the child nodes of the element ' +
           'with React ID `%s`.',
           updatedIndex,
@@ -137,7 +138,8 @@ var DOMChildrenOperations = {
       }
     }
 
-    for (var k = 0; update = updates[k]; k++) {
+    for (var k = 0; k < updates.length; k++) {
+      update = updates[k];
       switch (update.type) {
         case ReactMultiChildUpdateTypes.INSERT_MARKUP:
           insertChildAt(
diff --git a/src/browser/ui/dom/DOMProperty.js b/src/browser/ui/dom/DOMProperty.js
index dcc2ae50fe..30590a864e 100644
--- a/src/browser/ui/dom/DOMProperty.js
+++ b/src/browser/ui/dom/DOMProperty.js
@@ -12,7 +12,7 @@
 
 /*jslint bitwise: true */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/browser/ui/dom/DOMPropertyOperations.js b/src/browser/ui/dom/DOMPropertyOperations.js
index 631505becc..364c70644b 100644
--- a/src/browser/ui/dom/DOMPropertyOperations.js
+++ b/src/browser/ui/dom/DOMPropertyOperations.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var DOMProperty = require('DOMProperty');
 
diff --git a/src/browser/ui/dom/Danger.js b/src/browser/ui/dom/Danger.js
index 270d6d28bb..64df47bd94 100644
--- a/src/browser/ui/dom/Danger.js
+++ b/src/browser/ui/dom/Danger.js
@@ -12,7 +12,7 @@
 
 /*jslint evil: true, sub: true */
 
-"use strict";
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
@@ -82,7 +82,8 @@ var Danger = {
       // This for-in loop skips the holes of the sparse array. The order of
       // iteration should follow the order of assignment, which happens to match
       // numerical index order, but we don't rely on that.
-      for (var resultIndex in markupListByNodeName) {
+      var resultIndex;
+      for (resultIndex in markupListByNodeName) {
         if (markupListByNodeName.hasOwnProperty(resultIndex)) {
           var markup = markupListByNodeName[resultIndex];
 
@@ -103,8 +104,8 @@ var Danger = {
         emptyFunction // Do nothing special with <script> tags.
       );
 
-      for (i = 0; i < renderNodes.length; ++i) {
-        var renderNode = renderNodes[i];
+      for (var j = 0; j < renderNodes.length; ++j) {
+        var renderNode = renderNodes[j];
         if (renderNode.hasAttribute &&
             renderNode.hasAttribute(RESULT_INDEX_ATTR)) {
 
@@ -124,7 +125,7 @@ var Danger = {
 
         } else if (__DEV__) {
           console.error(
-            "Danger: Discarding unexpected node:",
+            'Danger: Discarding unexpected node:',
             renderNode
           );
         }
diff --git a/src/browser/ui/dom/HTMLDOMPropertyConfig.js b/src/browser/ui/dom/HTMLDOMPropertyConfig.js
index 1207f28add..468a8a8c8f 100644
--- a/src/browser/ui/dom/HTMLDOMPropertyConfig.js
+++ b/src/browser/ui/dom/HTMLDOMPropertyConfig.js
@@ -11,7 +11,7 @@
 
 /*jslint bitwise: true*/
 
-"use strict";
+'use strict';
 
 var DOMProperty = require('DOMProperty');
 var ExecutionEnvironment = require('ExecutionEnvironment');
@@ -160,12 +160,17 @@ var HTMLDOMPropertyConfig = {
     /**
      * Non-standard Properties
      */
-    autoCapitalize: null, // Supported in Mobile Safari for keyboard hints
-    autoCorrect: null, // Supported in Mobile Safari for keyboard hints
-    itemProp: MUST_USE_ATTRIBUTE, // Microdata: http://schema.org/docs/gs.html
-    itemScope: MUST_USE_ATTRIBUTE | HAS_BOOLEAN_VALUE, // Microdata: http://schema.org/docs/gs.html
-    itemType: MUST_USE_ATTRIBUTE, // Microdata: http://schema.org/docs/gs.html
-    property: null // Supports OG in meta tags
+    // autoCapitalize and autoCorrect are supported in Mobile Safari for
+    // keyboard hints.
+    autoCapitalize: null,
+    autoCorrect: null,
+    // itemProp, itemScope, itemType are for Microdata support. See
+    // http://schema.org/docs/gs.html
+    itemProp: MUST_USE_ATTRIBUTE,
+    itemScope: MUST_USE_ATTRIBUTE | HAS_BOOLEAN_VALUE,
+    itemType: MUST_USE_ATTRIBUTE,
+    // property is supported for OpenGraph in meta tags.
+    property: null
   },
   DOMAttributeNames: {
     acceptCharset: 'accept-charset',
diff --git a/src/browser/ui/dom/SVGDOMPropertyConfig.js b/src/browser/ui/dom/SVGDOMPropertyConfig.js
index 2f78f1d786..27e02296a0 100644
--- a/src/browser/ui/dom/SVGDOMPropertyConfig.js
+++ b/src/browser/ui/dom/SVGDOMPropertyConfig.js
@@ -11,7 +11,7 @@
 
 /*jslint bitwise: true*/
 
-"use strict";
+'use strict';
 
 var DOMProperty = require('DOMProperty');
 
diff --git a/src/browser/ui/dom/ViewportMetrics.js b/src/browser/ui/dom/ViewportMetrics.js
index 383dcb2ef6..17a5159f52 100644
--- a/src/browser/ui/dom/ViewportMetrics.js
+++ b/src/browser/ui/dom/ViewportMetrics.js
@@ -9,7 +9,7 @@
  * @providesModule ViewportMetrics
  */
 
-"use strict";
+'use strict';
 
 var ViewportMetrics = {
 
diff --git a/src/browser/ui/dom/__tests__/CSSProperty-test.js b/src/browser/ui/dom/__tests__/CSSProperty-test.js
index c16ff9bf5a..ab8cb5c34a 100644
--- a/src/browser/ui/dom/__tests__/CSSProperty-test.js
+++ b/src/browser/ui/dom/__tests__/CSSProperty-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 describe('CSSProperty', function() {
   var CSSProperty;
diff --git a/src/browser/ui/dom/__tests__/CSSPropertyOperations-test.js b/src/browser/ui/dom/__tests__/CSSPropertyOperations-test.js
index a79d7732c5..e7f0519138 100644
--- a/src/browser/ui/dom/__tests__/CSSPropertyOperations-test.js
+++ b/src/browser/ui/dom/__tests__/CSSPropertyOperations-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 
diff --git a/src/browser/ui/dom/__tests__/DOMPropertyOperations-test.js b/src/browser/ui/dom/__tests__/DOMPropertyOperations-test.js
index 8b0c27850b..9507a788e0 100644
--- a/src/browser/ui/dom/__tests__/DOMPropertyOperations-test.js
+++ b/src/browser/ui/dom/__tests__/DOMPropertyOperations-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('DOMPropertyOperations', function() {
   var DOMPropertyOperations;
diff --git a/src/browser/ui/dom/__tests__/Danger-test.js b/src/browser/ui/dom/__tests__/Danger-test.js
index 69f71c4655..f14dcfab9f 100644
--- a/src/browser/ui/dom/__tests__/Danger-test.js
+++ b/src/browser/ui/dom/__tests__/Danger-test.js
@@ -10,7 +10,7 @@
  */
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var instantiateReactComponent = require('instantiateReactComponent');
diff --git a/src/browser/ui/dom/__tests__/getNodeForCharacterOffset-test.js b/src/browser/ui/dom/__tests__/getNodeForCharacterOffset-test.js
index 3e1ab045c1..5d9f6e672e 100644
--- a/src/browser/ui/dom/__tests__/getNodeForCharacterOffset-test.js
+++ b/src/browser/ui/dom/__tests__/getNodeForCharacterOffset-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 var getTestDocument = require('getTestDocument');
 
diff --git a/src/browser/ui/dom/components/AutoFocusMixin.js b/src/browser/ui/dom/components/AutoFocusMixin.js
index a11bdd9999..46322d58ff 100644
--- a/src/browser/ui/dom/components/AutoFocusMixin.js
+++ b/src/browser/ui/dom/components/AutoFocusMixin.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var focusNode = require('focusNode');
 
diff --git a/src/browser/ui/dom/components/LinkedValueUtils.js b/src/browser/ui/dom/components/LinkedValueUtils.js
index 060db3249d..c1235b13e3 100644
--- a/src/browser/ui/dom/components/LinkedValueUtils.js
+++ b/src/browser/ui/dom/components/LinkedValueUtils.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ReactPropTypes = require('ReactPropTypes');
 
@@ -81,7 +81,7 @@ var LinkedValueUtils = {
             props.onChange ||
             props.readOnly ||
             props.disabled) {
-          return;
+          return null;
         }
         return new Error(
           'You provided a `value` prop to a form field without an ' +
@@ -95,7 +95,7 @@ var LinkedValueUtils = {
             props.onChange ||
             props.readOnly ||
             props.disabled) {
-          return;
+          return null;
         }
         return new Error(
           'You provided a `checked` prop to a form field without an ' +
diff --git a/src/browser/ui/dom/components/LocalEventTrapMixin.js b/src/browser/ui/dom/components/LocalEventTrapMixin.js
index 493658ea43..d466c9df2d 100644
--- a/src/browser/ui/dom/components/LocalEventTrapMixin.js
+++ b/src/browser/ui/dom/components/LocalEventTrapMixin.js
@@ -9,7 +9,7 @@
  * @providesModule LocalEventTrapMixin
  */
 
-"use strict";
+'use strict';
 
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
 
diff --git a/src/browser/ui/dom/components/ReactDOMButton.js b/src/browser/ui/dom/components/ReactDOMButton.js
index 79206afe9f..b77e2ad67c 100644
--- a/src/browser/ui/dom/components/ReactDOMButton.js
+++ b/src/browser/ui/dom/components/ReactDOMButton.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMButton
  */
 
-"use strict";
+'use strict';
 
 var AutoFocusMixin = require('AutoFocusMixin');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
diff --git a/src/browser/ui/dom/components/ReactDOMForm.js b/src/browser/ui/dom/components/ReactDOMForm.js
index 20c2b038cc..d9ab431ac6 100644
--- a/src/browser/ui/dom/components/ReactDOMForm.js
+++ b/src/browser/ui/dom/components/ReactDOMForm.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMForm
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var LocalEventTrapMixin = require('LocalEventTrapMixin');
diff --git a/src/browser/ui/dom/components/ReactDOMImg.js b/src/browser/ui/dom/components/ReactDOMImg.js
index 5a0495f107..f14b25d034 100644
--- a/src/browser/ui/dom/components/ReactDOMImg.js
+++ b/src/browser/ui/dom/components/ReactDOMImg.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMImg
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var LocalEventTrapMixin = require('LocalEventTrapMixin');
diff --git a/src/browser/ui/dom/components/ReactDOMInput.js b/src/browser/ui/dom/components/ReactDOMInput.js
index 50026420a6..52dea17f13 100644
--- a/src/browser/ui/dom/components/ReactDOMInput.js
+++ b/src/browser/ui/dom/components/ReactDOMInput.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMInput
  */
 
-"use strict";
+'use strict';
 
 var AutoFocusMixin = require('AutoFocusMixin');
 var DOMPropertyOperations = require('DOMPropertyOperations');
diff --git a/src/browser/ui/dom/components/ReactDOMOption.js b/src/browser/ui/dom/components/ReactDOMOption.js
index 1657703e31..e66a708bae 100644
--- a/src/browser/ui/dom/components/ReactDOMOption.js
+++ b/src/browser/ui/dom/components/ReactDOMOption.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMOption
  */
 
-"use strict";
+'use strict';
 
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
diff --git a/src/browser/ui/dom/components/ReactDOMSelect.js b/src/browser/ui/dom/components/ReactDOMSelect.js
index e1ac3d68d9..aa41aeddf2 100644
--- a/src/browser/ui/dom/components/ReactDOMSelect.js
+++ b/src/browser/ui/dom/components/ReactDOMSelect.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMSelect
  */
 
-"use strict";
+'use strict';
 
 var AutoFocusMixin = require('AutoFocusMixin');
 var LinkedValueUtils = require('LinkedValueUtils');
@@ -39,7 +39,7 @@ function updateOptionsIfPendingUpdateAndMounted() {
  */
 function selectValueType(props, propName, componentName) {
   if (props[propName] == null) {
-    return;
+    return null;
   }
   if (props.multiple) {
     if (!Array.isArray(props[propName])) {
diff --git a/src/browser/ui/dom/components/ReactDOMTextarea.js b/src/browser/ui/dom/components/ReactDOMTextarea.js
index e0f7afee60..66ebf40f6c 100644
--- a/src/browser/ui/dom/components/ReactDOMTextarea.js
+++ b/src/browser/ui/dom/components/ReactDOMTextarea.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDOMTextarea
  */
 
-"use strict";
+'use strict';
 
 var AutoFocusMixin = require('AutoFocusMixin');
 var DOMPropertyOperations = require('DOMPropertyOperations');
diff --git a/src/browser/ui/dom/components/__tests__/ReactDOMButton-test.js b/src/browser/ui/dom/components/__tests__/ReactDOMButton-test.js
index 04a9a85731..5028ac83f9 100644
--- a/src/browser/ui/dom/components/__tests__/ReactDOMButton-test.js
+++ b/src/browser/ui/dom/components/__tests__/ReactDOMButton-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 /*jshint evil:true */
 
diff --git a/src/browser/ui/dom/components/__tests__/ReactDOMInput-test.js b/src/browser/ui/dom/components/__tests__/ReactDOMInput-test.js
index bdda637ab3..16b5d7352e 100644
--- a/src/browser/ui/dom/components/__tests__/ReactDOMInput-test.js
+++ b/src/browser/ui/dom/components/__tests__/ReactDOMInput-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 /*jshint evil:true */
 
diff --git a/src/browser/ui/dom/components/__tests__/ReactDOMSelect-test.js b/src/browser/ui/dom/components/__tests__/ReactDOMSelect-test.js
index 4f99f99bf9..df55a19abc 100644
--- a/src/browser/ui/dom/components/__tests__/ReactDOMSelect-test.js
+++ b/src/browser/ui/dom/components/__tests__/ReactDOMSelect-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 /*jshint evil:true */
 
diff --git a/src/browser/ui/dom/components/__tests__/ReactDOMTextarea-test.js b/src/browser/ui/dom/components/__tests__/ReactDOMTextarea-test.js
index 7517691913..8b139e7028 100644
--- a/src/browser/ui/dom/components/__tests__/ReactDOMTextarea-test.js
+++ b/src/browser/ui/dom/components/__tests__/ReactDOMTextarea-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var emptyFunction = require('emptyFunction');
 var mocks = require('mocks');
diff --git a/src/browser/ui/dom/components/createFullPageComponent.js b/src/browser/ui/dom/components/createFullPageComponent.js
index f9dbd16592..e098115275 100644
--- a/src/browser/ui/dom/components/createFullPageComponent.js
+++ b/src/browser/ui/dom/components/createFullPageComponent.js
@@ -10,7 +10,7 @@
  * @typechecks
  */
 
-"use strict";
+'use strict';
 
 // Defeat circular references by requiring this directly.
 var ReactClass = require('ReactClass');
diff --git a/src/browser/ui/dom/dangerousStyleValue.js b/src/browser/ui/dom/dangerousStyleValue.js
index b98201d008..909d908266 100644
--- a/src/browser/ui/dom/dangerousStyleValue.js
+++ b/src/browser/ui/dom/dangerousStyleValue.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var CSSProperty = require('CSSProperty');
 
diff --git a/src/browser/ui/dom/getEventCharCode.js b/src/browser/ui/dom/getEventCharCode.js
index ff2a912265..7d2e399211 100644
--- a/src/browser/ui/dom/getEventCharCode.js
+++ b/src/browser/ui/dom/getEventCharCode.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * `charCode` represents the actual "character code" and is safe to use with
diff --git a/src/browser/ui/dom/getEventKey.js b/src/browser/ui/dom/getEventKey.js
index 11ac2b180f..7e2af3ebab 100644
--- a/src/browser/ui/dom/getEventKey.js
+++ b/src/browser/ui/dom/getEventKey.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var getEventCharCode = require('getEventCharCode');
 
diff --git a/src/browser/ui/dom/getEventModifierState.js b/src/browser/ui/dom/getEventModifierState.js
index 24e0b749a4..609a3a4338 100644
--- a/src/browser/ui/dom/getEventModifierState.js
+++ b/src/browser/ui/dom/getEventModifierState.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * Translation from modifier key to the associated property in the event.
diff --git a/src/browser/ui/dom/getEventTarget.js b/src/browser/ui/dom/getEventTarget.js
index 27efdd5997..81ab810f03 100644
--- a/src/browser/ui/dom/getEventTarget.js
+++ b/src/browser/ui/dom/getEventTarget.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * Gets the target node from a native browser event by accounting for
diff --git a/src/browser/ui/dom/getNodeForCharacterOffset.js b/src/browser/ui/dom/getNodeForCharacterOffset.js
index 22b54adb20..8128a3bc88 100644
--- a/src/browser/ui/dom/getNodeForCharacterOffset.js
+++ b/src/browser/ui/dom/getNodeForCharacterOffset.js
@@ -9,7 +9,7 @@
  * @providesModule getNodeForCharacterOffset
  */
 
-"use strict";
+'use strict';
 
 /**
  * Given any node return the first leaf node without children.
@@ -53,7 +53,7 @@ function getNodeForCharacterOffset(root, offset) {
   var nodeEnd = 0;
 
   while (node) {
-    if (node.nodeType == 3) {
+    if (node.nodeType === 3) {
       nodeEnd = nodeStart + node.textContent.length;
 
       if (nodeStart <= offset && nodeEnd >= offset) {
diff --git a/src/browser/ui/dom/getTextContentAccessor.js b/src/browser/ui/dom/getTextContentAccessor.js
index 59a14d9b38..1777551418 100644
--- a/src/browser/ui/dom/getTextContentAccessor.js
+++ b/src/browser/ui/dom/getTextContentAccessor.js
@@ -9,7 +9,7 @@
  * @providesModule getTextContentAccessor
  */
 
-"use strict";
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
diff --git a/src/browser/ui/dom/isEventSupported.js b/src/browser/ui/dom/isEventSupported.js
index 77cb704ea8..1bbea28178 100644
--- a/src/browser/ui/dom/isEventSupported.js
+++ b/src/browser/ui/dom/isEventSupported.js
@@ -9,7 +9,7 @@
  * @providesModule isEventSupported
  */
 
-"use strict";
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
diff --git a/src/browser/ui/dom/setInnerHTML.js b/src/browser/ui/dom/setInnerHTML.js
index c2318ae4aa..729f39caf1 100644
--- a/src/browser/ui/dom/setInnerHTML.js
+++ b/src/browser/ui/dom/setInnerHTML.js
@@ -9,7 +9,9 @@
  * @providesModule setInnerHTML
  */
 
-"use strict";
+/* globals MSApp */
+
+'use strict';
 
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
diff --git a/src/browser/ui/getReactRootElementInContainer.js b/src/browser/ui/getReactRootElementInContainer.js
index 5fb031ddce..6157543dc0 100644
--- a/src/browser/ui/getReactRootElementInContainer.js
+++ b/src/browser/ui/getReactRootElementInContainer.js
@@ -9,7 +9,7 @@
  * @providesModule getReactRootElementInContainer
  */
 
-"use strict";
+'use strict';
 
 var DOC_NODE_TYPE = 9;
 
diff --git a/src/classic/__tests__/ReactContextValidator-test.js b/src/classic/__tests__/ReactContextValidator-test.js
index 3f9f8c017b..bc504a3531 100644
--- a/src/classic/__tests__/ReactContextValidator-test.js
+++ b/src/classic/__tests__/ReactContextValidator-test.js
@@ -15,7 +15,7 @@
 // test suite but I'll leave it here to indicate that this is an issue that
 // needs to be fixed.
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTestUtils;
diff --git a/src/classic/class/ReactClass.js b/src/classic/class/ReactClass.js
index 09dd3452e9..7382bc9f46 100644
--- a/src/classic/class/ReactClass.js
+++ b/src/classic/class/ReactClass.js
@@ -9,7 +9,7 @@
  * @providesModule ReactClass
  */
 
-"use strict";
+'use strict';
 
 var ReactComponentBase = require('ReactComponentBase');
 var ReactElement = require('ReactElement');
@@ -382,7 +382,7 @@ function validateTypeDef(Constructor, typeDef, location) {
   for (var propName in typeDef) {
     if (typeDef.hasOwnProperty(propName)) {
       invariant(
-        typeof typeDef[propName] == 'function',
+        typeof typeDef[propName] === 'function',
         '%s: %s type `%s` is invalid; it must be a function, usually from ' +
         'React.PropTypes.',
         Constructor.displayName || 'ReactClass',
@@ -642,6 +642,7 @@ function bindAutoBindMethod(component, method) {
     boundMethod.__reactBoundArguments = null;
     var componentName = component.constructor.displayName;
     var _bind = boundMethod.bind;
+    /* eslint-disable block-scoped-var, no-undef */
     boundMethod.bind = function(newThis, ...args) {
       // User is trying to bind() an autobound method; we effectively will
       // ignore the value of "this" that the user is trying to use, so
@@ -666,6 +667,7 @@ function bindAutoBindMethod(component, method) {
       reboundMethod.__reactBoundMethod = method;
       reboundMethod.__reactBoundArguments = args;
       return reboundMethod;
+      /* eslint-enable */
     };
   }
   return boundMethod;
diff --git a/src/classic/class/ReactDoNotBindDeprecated.js b/src/classic/class/ReactDoNotBindDeprecated.js
index 054636a308..5ee6efcc39 100644
--- a/src/classic/class/ReactDoNotBindDeprecated.js
+++ b/src/classic/class/ReactDoNotBindDeprecated.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDoNotBindDeprecated
  */
 
-"use strict";
+'use strict';
 
 var ReactDoNotBindDeprecated = {
   /**
diff --git a/src/classic/class/__tests__/ReactBind-test.js b/src/classic/class/__tests__/ReactBind-test.js
index e5a507b3ee..4f9acb2141 100644
--- a/src/classic/class/__tests__/ReactBind-test.js
+++ b/src/classic/class/__tests__/ReactBind-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 /*global global:true*/
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 var React = require('React');
diff --git a/src/classic/class/__tests__/ReactClass-test.js b/src/classic/class/__tests__/ReactClass-test.js
index a0100400f8..2adf2fbe75 100644
--- a/src/classic/class/__tests__/ReactClass-test.js
+++ b/src/classic/class/__tests__/ReactClass-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 
diff --git a/src/classic/class/__tests__/ReactClassMixin-test.js b/src/classic/class/__tests__/ReactClassMixin-test.js
index 1db776f590..602f060bf8 100644
--- a/src/classic/class/__tests__/ReactClassMixin-test.js
+++ b/src/classic/class/__tests__/ReactClassMixin-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 
diff --git a/src/classic/element/ReactElement.js b/src/classic/element/ReactElement.js
index e00d36c7bf..46233c86e8 100644
--- a/src/classic/element/ReactElement.js
+++ b/src/classic/element/ReactElement.js
@@ -9,7 +9,7 @@
  * @providesModule ReactElement
  */
 
-"use strict";
+'use strict';
 
 var ReactContext = require('ReactContext');
 var ReactCurrentOwner = require('ReactCurrentOwner');
diff --git a/src/classic/element/ReactElementValidator.js b/src/classic/element/ReactElementValidator.js
index 1aedd8cc98..e13d81c70c 100644
--- a/src/classic/element/ReactElementValidator.js
+++ b/src/classic/element/ReactElementValidator.js
@@ -16,7 +16,7 @@
  * that support it.
  */
 
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactPropTypeLocations = require('ReactPropTypeLocations');
diff --git a/src/classic/element/__tests__/ReactElement-test.js b/src/classic/element/__tests__/ReactElement-test.js
index 633fb56ef7..b9cff30e97 100644
--- a/src/classic/element/__tests__/ReactElement-test.js
+++ b/src/classic/element/__tests__/ReactElement-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 // NOTE: We're explicitly not using JSX in this file. This is intended to test
 // classic JS without JSX.
diff --git a/src/classic/element/__tests__/ReactElementValidator-test.js b/src/classic/element/__tests__/ReactElementValidator-test.js
index bccfa09c7c..311be0377b 100644
--- a/src/classic/element/__tests__/ReactElementValidator-test.js
+++ b/src/classic/element/__tests__/ReactElementValidator-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 // NOTE: We're explicitly not using JSX in this file. This is intended to test
 // classic JS without JSX.
diff --git a/src/classic/types/ReactPropTypeLocationNames.js b/src/classic/types/ReactPropTypeLocationNames.js
index 30d0ccb5bb..a8b8e97a40 100644
--- a/src/classic/types/ReactPropTypeLocationNames.js
+++ b/src/classic/types/ReactPropTypeLocationNames.js
@@ -9,7 +9,7 @@
  * @providesModule ReactPropTypeLocationNames
  */
 
-"use strict";
+'use strict';
 
 var ReactPropTypeLocationNames = {};
 
diff --git a/src/classic/types/ReactPropTypeLocations.js b/src/classic/types/ReactPropTypeLocations.js
index df4047f823..155faf28f7 100644
--- a/src/classic/types/ReactPropTypeLocations.js
+++ b/src/classic/types/ReactPropTypeLocations.js
@@ -9,7 +9,7 @@
  * @providesModule ReactPropTypeLocations
  */
 
-"use strict";
+'use strict';
 
 var keyMirror = require('keyMirror');
 
diff --git a/src/classic/types/ReactPropTypes.js b/src/classic/types/ReactPropTypes.js
index d1e0e55fd2..bdf31ef130 100644
--- a/src/classic/types/ReactPropTypes.js
+++ b/src/classic/types/ReactPropTypes.js
@@ -9,7 +9,7 @@
  * @providesModule ReactPropTypes
  */
 
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactPropTypeLocationNames = require('ReactPropTypeLocationNames');
@@ -98,6 +98,7 @@ function createChainableTypeChecker(validate) {
           `\`${componentName}\`.`
         );
       }
+      return null;
     } else {
       return validate(props, propName, componentName, location);
     }
@@ -125,12 +126,13 @@ function createPrimitiveTypeChecker(expectedType) {
         `supplied to \`${componentName}\`, expected \`${expectedType}\`.`
       );
     }
+    return null;
   }
   return createChainableTypeChecker(validate);
 }
 
 function createAnyTypeChecker() {
-  return createChainableTypeChecker(emptyFunction.thatReturns());
+  return createChainableTypeChecker(emptyFunction.thatReturns(null));
 }
 
 function createArrayOfTypeChecker(typeChecker) {
@@ -150,6 +152,7 @@ function createArrayOfTypeChecker(typeChecker) {
         return error;
       }
     }
+    return null;
   }
   return createChainableTypeChecker(validate);
 }
@@ -163,6 +166,7 @@ function createElementTypeChecker() {
         `\`${componentName}\`, expected a ReactElement.`
       );
     }
+    return null;
   }
   return createChainableTypeChecker(validate);
 }
@@ -177,6 +181,7 @@ function createInstanceTypeChecker(expectedClass) {
         `\`${componentName}\`, expected instance of \`${expectedClassName}\`.`
       );
     }
+    return null;
   }
   return createChainableTypeChecker(validate);
 }
@@ -186,7 +191,7 @@ function createEnumTypeChecker(expectedValues) {
     var propValue = props[propName];
     for (var i = 0; i < expectedValues.length; i++) {
       if (propValue === expectedValues[i]) {
-        return;
+        return null;
       }
     }
 
@@ -219,6 +224,7 @@ function createObjectOfTypeChecker(typeChecker) {
         }
       }
     }
+    return null;
   }
   return createChainableTypeChecker(validate);
 }
@@ -228,7 +234,7 @@ function createUnionTypeChecker(arrayOfTypeCheckers) {
     for (var i = 0; i < arrayOfTypeCheckers.length; i++) {
       var checker = arrayOfTypeCheckers[i];
       if (checker(props, propName, componentName, location) == null) {
-        return;
+        return null;
       }
     }
 
@@ -250,6 +256,7 @@ function createNodeChecker() {
         `\`${componentName}\`, expected a ReactNode.`
       );
     }
+    return null;
   }
   return createChainableTypeChecker(validate);
 }
@@ -275,12 +282,13 @@ function createShapeTypeChecker(shapeTypes) {
         return error;
       }
     }
+    return null;
   }
   return createChainableTypeChecker(validate, 'expected `object`');
 }
 
 function isNode(propValue) {
-  switch(typeof propValue) {
+  switch (typeof propValue) {
     case 'number':
     case 'string':
       return true;
diff --git a/src/classic/types/__tests__/ReactPropTypes-test.js b/src/classic/types/__tests__/ReactPropTypes-test.js
index fee67c7f7d..fe0ad4a340 100644
--- a/src/classic/types/__tests__/ReactPropTypes-test.js
+++ b/src/classic/types/__tests__/ReactPropTypes-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var PropTypes;
 var React;
@@ -41,7 +41,7 @@ function typeCheckPass(declaration, value) {
     'testComponent',
     ReactPropTypeLocations.prop
   );
-  expect(error).toBe(undefined);
+  expect(error).toBe(null);
 }
 
 describe('ReactPropTypes', function() {
diff --git a/src/core/ReactChildReconciler.js b/src/core/ReactChildReconciler.js
index 209d3f9ad6..47b11dca5f 100644
--- a/src/core/ReactChildReconciler.js
+++ b/src/core/ReactChildReconciler.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var flattenChildren = require('flattenChildren');
 var instantiateReactComponent = require('instantiateReactComponent');
@@ -67,7 +67,7 @@ var ReactChildReconciler = {
     // can quickly bailout if nothing has changed.
     var nextChildren = flattenChildren(nextNestedChildNodes);
     if (!nextChildren && !prevChildren) {
-      return;
+      return null;
     }
     var name;
     for (name in nextChildren) {
diff --git a/src/core/ReactComponent.js b/src/core/ReactComponent.js
index 678aa70333..26492bf101 100644
--- a/src/core/ReactComponent.js
+++ b/src/core/ReactComponent.js
@@ -9,7 +9,7 @@
  * @providesModule ReactComponent
  */
 
-"use strict";
+'use strict';
 
 var ReactOwner = require('ReactOwner');
 var ReactRef = require('ReactRef');
diff --git a/src/core/ReactComponentEnvironment.js b/src/core/ReactComponentEnvironment.js
index 48f3b50d06..9241dafdb9 100644
--- a/src/core/ReactComponentEnvironment.js
+++ b/src/core/ReactComponentEnvironment.js
@@ -9,7 +9,7 @@
  * @providesModule ReactComponentEnvironment
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
@@ -50,7 +50,7 @@ var ReactComponentEnvironment = {
         environment.processChildrenUpdates;
       injected = true;
     }
-  },
+  }
 
 };
 
diff --git a/src/core/ReactCompositeComponent.js b/src/core/ReactCompositeComponent.js
index df365ea911..5f818729c6 100644
--- a/src/core/ReactCompositeComponent.js
+++ b/src/core/ReactCompositeComponent.js
@@ -9,7 +9,7 @@
  * @providesModule ReactCompositeComponent
  */
 
-"use strict";
+'use strict';
 
 var ReactComponent = require('ReactComponent');
 var ReactComponentEnvironment = require('ReactComponentEnvironment');
@@ -746,7 +746,7 @@ var ReactCompositeComponentMixin = assign({},
       inst.shouldComponentUpdate(nextProps, nextState, nextContext);
 
     if (__DEV__) {
-      if (typeof shouldUpdate === "undefined") {
+      if (typeof shouldUpdate === 'undefined') {
         console.warn(
           (this.getName() || 'ReactCompositeComponent') +
           '.shouldComponentUpdate(): Returned undefined instead of a ' +
@@ -935,7 +935,7 @@ var ReactCompositeComponentMixin = assign({},
     var refs = this.getPublicInstance().refs;
     delete refs[ref];
   },
- 
+
   /**
    * Get a text description of the component that can be used to identify it
    * in error messages.
diff --git a/src/core/ReactContext.js b/src/core/ReactContext.js
index 449796988e..e1c655e955 100644
--- a/src/core/ReactContext.js
+++ b/src/core/ReactContext.js
@@ -9,7 +9,7 @@
  * @providesModule ReactContext
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 var emptyObject = require('emptyObject');
diff --git a/src/core/ReactCurrentOwner.js b/src/core/ReactCurrentOwner.js
index b9430574d2..4b0508dbfe 100644
--- a/src/core/ReactCurrentOwner.js
+++ b/src/core/ReactCurrentOwner.js
@@ -9,7 +9,7 @@
  * @providesModule ReactCurrentOwner
  */
 
-"use strict";
+'use strict';
 
 /**
  * Keeps track of the current owner.
diff --git a/src/core/ReactDefaultBatchingStrategy.js b/src/core/ReactDefaultBatchingStrategy.js
index 9d1bd36392..37e64a36d8 100644
--- a/src/core/ReactDefaultBatchingStrategy.js
+++ b/src/core/ReactDefaultBatchingStrategy.js
@@ -9,7 +9,7 @@
  * @providesModule ReactDefaultBatchingStrategy
  */
 
-"use strict";
+'use strict';
 
 var ReactUpdates = require('ReactUpdates');
 var Transaction = require('Transaction');
diff --git a/src/core/ReactEmptyComponent.js b/src/core/ReactEmptyComponent.js
index d40c28d79f..c2e21ed518 100644
--- a/src/core/ReactEmptyComponent.js
+++ b/src/core/ReactEmptyComponent.js
@@ -9,7 +9,7 @@
  * @providesModule ReactEmptyComponent
  */
 
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactInstanceMap = require('ReactInstanceMap');
diff --git a/src/core/ReactEventEmitterMixin.js b/src/core/ReactEventEmitterMixin.js
index 1ac8d3b084..8d183442a6 100644
--- a/src/core/ReactEventEmitterMixin.js
+++ b/src/core/ReactEventEmitterMixin.js
@@ -9,7 +9,7 @@
  * @providesModule ReactEventEmitterMixin
  */
 
-"use strict";
+'use strict';
 
 var EventPluginHub = require('EventPluginHub');
 
diff --git a/src/core/ReactInstanceHandles.js b/src/core/ReactInstanceHandles.js
index dd68c55fd3..ced9aae23a 100644
--- a/src/core/ReactInstanceHandles.js
+++ b/src/core/ReactInstanceHandles.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ReactRootIndex = require('ReactRootIndex');
 
@@ -115,7 +115,8 @@ function getNextDescendantID(ancestorID, destinationID) {
   // Skip over the ancestor and the immediate separator. Traverse until we hit
   // another separator or we reach the end of `destinationID`.
   var start = ancestorID.length + SEPARATOR_LENGTH;
-  for (var i = start; i < destinationID.length; i++) {
+  var i;
+  for (i = start; i < destinationID.length; i++) {
     if (isBoundary(destinationID, i)) {
       break;
     }
diff --git a/src/core/ReactInstanceMap.js b/src/core/ReactInstanceMap.js
index 6c6209eb94..e674d2ff00 100644
--- a/src/core/ReactInstanceMap.js
+++ b/src/core/ReactInstanceMap.js
@@ -9,7 +9,7 @@
  * @providesModule ReactInstanceMap
  */
 
-"use strict";
+'use strict';
 
 /**
  * `ReactInstanceMap` maintains a mapping from a public facing stateful
diff --git a/src/core/ReactMultiChild.js b/src/core/ReactMultiChild.js
index 7960c22ab0..758292125e 100644
--- a/src/core/ReactMultiChild.js
+++ b/src/core/ReactMultiChild.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ReactComponentEnvironment = require('ReactComponentEnvironment');
 var ReactMultiChildUpdateTypes = require('ReactMultiChildUpdateTypes');
@@ -226,7 +226,11 @@ var ReactMultiChild = {
       } finally {
         updateDepth--;
         if (!updateDepth) {
-          errorThrown ? clearQueue() : processQueue();
+          if (errorThrown) {
+            clearQueue();
+          } else {
+            processQueue();
+          }
         }
       }
     },
@@ -247,8 +251,13 @@ var ReactMultiChild = {
       } finally {
         updateDepth--;
         if (!updateDepth) {
-          errorThrown ? clearQueue() : processQueue();
+          if (errorThrown) {
+            clearQueue();
+          } else {
+            processQueue();
+          }
         }
+
       }
     },
 
diff --git a/src/core/ReactMultiChildUpdateTypes.js b/src/core/ReactMultiChildUpdateTypes.js
index fce50f9018..62c54ecb82 100644
--- a/src/core/ReactMultiChildUpdateTypes.js
+++ b/src/core/ReactMultiChildUpdateTypes.js
@@ -9,7 +9,7 @@
  * @providesModule ReactMultiChildUpdateTypes
  */
 
-"use strict";
+'use strict';
 
 var keyMirror = require('keyMirror');
 
diff --git a/src/core/ReactNativeComponent.js b/src/core/ReactNativeComponent.js
index 3f03fa1c51..fb2cde2644 100644
--- a/src/core/ReactNativeComponent.js
+++ b/src/core/ReactNativeComponent.js
@@ -9,7 +9,7 @@
  * @providesModule ReactNativeComponent
  */
 
-"use strict";
+'use strict';
 
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
diff --git a/src/core/ReactOwner.js b/src/core/ReactOwner.js
index 29da2705a9..e8ecd0ad92 100644
--- a/src/core/ReactOwner.js
+++ b/src/core/ReactOwner.js
@@ -9,7 +9,7 @@
  * @providesModule ReactOwner
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/core/ReactPropTransferer.js b/src/core/ReactPropTransferer.js
index 6b9edc364e..7b10eb722e 100644
--- a/src/core/ReactPropTransferer.js
+++ b/src/core/ReactPropTransferer.js
@@ -9,7 +9,7 @@
  * @providesModule ReactPropTransferer
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 var emptyFunction = require('emptyFunction');
@@ -101,7 +101,7 @@ var ReactPropTransferer = {
    */
   mergeProps: function(oldProps, newProps) {
     return transferInto(assign({}, oldProps), newProps);
-  },
+  }
 
 };
 
diff --git a/src/core/ReactRef.js b/src/core/ReactRef.js
index d99a91a4cc..44042e7e47 100644
--- a/src/core/ReactRef.js
+++ b/src/core/ReactRef.js
@@ -9,7 +9,7 @@
  * @providesModule ReactRef
  */
 
-"use strict";
+'use strict';
 
 var ReactUpdates = require('ReactUpdates');
 
diff --git a/src/core/ReactRootIndex.js b/src/core/ReactRootIndex.js
index 3fdd0921c5..c9cc8375a9 100644
--- a/src/core/ReactRootIndex.js
+++ b/src/core/ReactRootIndex.js
@@ -10,7 +10,7 @@
  * @typechecks
  */
 
-"use strict";
+'use strict';
 
 var ReactRootIndexInjection = {
   /**
diff --git a/src/core/ReactStateSetters.js b/src/core/ReactStateSetters.js
index bbe4742705..3c9c4ea925 100644
--- a/src/core/ReactStateSetters.js
+++ b/src/core/ReactStateSetters.js
@@ -9,7 +9,7 @@
  * @providesModule ReactStateSetters
  */
 
-"use strict";
+'use strict';
 
 var ReactStateSetters = {
   /**
diff --git a/src/core/ReactUpdates.js b/src/core/ReactUpdates.js
index 601d6a268c..3bbb40215f 100644
--- a/src/core/ReactUpdates.js
+++ b/src/core/ReactUpdates.js
@@ -9,7 +9,7 @@
  * @providesModule ReactUpdates
  */
 
-"use strict";
+'use strict';
 
 var CallbackQueue = require('CallbackQueue');
 var PooledClass = require('PooledClass');
@@ -192,7 +192,7 @@ flushBatchedUpdates = ReactPerf.measure(
  */
 function enqueueUpdate(component, callback) {
   invariant(
-    !callback || typeof callback === "function",
+    !callback || typeof callback === 'function',
     'enqueueUpdate(...): You called `setProps`, `replaceProps`, ' +
     '`setState`, `replaceState`, or `forceUpdate` with a callback that ' +
     'isn\'t callable.'
diff --git a/src/core/__tests__/ReactComponent-test.js b/src/core/__tests__/ReactComponent-test.js
index 31b15549c8..67b9c344ae 100644
--- a/src/core/__tests__/ReactComponent-test.js
+++ b/src/core/__tests__/ReactComponent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactInstanceMap;
diff --git a/src/core/__tests__/ReactComponentLifeCycle-test.js b/src/core/__tests__/ReactComponentLifeCycle-test.js
index 63692a77ff..8c108f1c80 100644
--- a/src/core/__tests__/ReactComponentLifeCycle-test.js
+++ b/src/core/__tests__/ReactComponentLifeCycle-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var keyMirror = require('keyMirror');
 
diff --git a/src/core/__tests__/ReactCompositeComponent-test.js b/src/core/__tests__/ReactCompositeComponent-test.js
index 4cb128842d..3de21e762c 100644
--- a/src/core/__tests__/ReactCompositeComponent-test.js
+++ b/src/core/__tests__/ReactCompositeComponent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var ChildUpdates;
 var MorphingComponent;
diff --git a/src/core/__tests__/ReactCompositeComponentDOMMinimalism-test.js b/src/core/__tests__/ReactCompositeComponentDOMMinimalism-test.js
index 3d4dd6b55e..9bc22e0910 100644
--- a/src/core/__tests__/ReactCompositeComponentDOMMinimalism-test.js
+++ b/src/core/__tests__/ReactCompositeComponentDOMMinimalism-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 // Requires
 var React;
diff --git a/src/core/__tests__/ReactCompositeComponentError-test.js b/src/core/__tests__/ReactCompositeComponentError-test.js
index 130bbf70bb..14a6359cb6 100644
--- a/src/core/__tests__/ReactCompositeComponentError-test.js
+++ b/src/core/__tests__/ReactCompositeComponentError-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactTestUtils = require('ReactTestUtils');
diff --git a/src/core/__tests__/ReactCompositeComponentState-test.js b/src/core/__tests__/ReactCompositeComponentState-test.js
index 10fa09a1bf..73930f1dc5 100644
--- a/src/core/__tests__/ReactCompositeComponentState-test.js
+++ b/src/core/__tests__/ReactCompositeComponentState-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 
diff --git a/src/core/__tests__/ReactEmptyComponent-test.js b/src/core/__tests__/ReactEmptyComponent-test.js
index 962cecdbca..575f734319 100644
--- a/src/core/__tests__/ReactEmptyComponent-test.js
+++ b/src/core/__tests__/ReactEmptyComponent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactEmptyComponent;
diff --git a/src/core/__tests__/ReactIdentity-test.js b/src/core/__tests__/ReactIdentity-test.js
index 088c6ec0b1..722b9bc8e5 100644
--- a/src/core/__tests__/ReactIdentity-test.js
+++ b/src/core/__tests__/ReactIdentity-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTestUtils;
diff --git a/src/core/__tests__/ReactInstanceHandles-test.js b/src/core/__tests__/ReactInstanceHandles-test.js
index bf2a71def6..12165e78ac 100644
--- a/src/core/__tests__/ReactInstanceHandles-test.js
+++ b/src/core/__tests__/ReactInstanceHandles-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactInstanceMap = require('ReactInstanceMap');
diff --git a/src/core/__tests__/ReactMockedComponent-test.js b/src/core/__tests__/ReactMockedComponent-test.js
index c0a288c568..4688548a2a 100644
--- a/src/core/__tests__/ReactMockedComponent-test.js
+++ b/src/core/__tests__/ReactMockedComponent-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactComponent;
diff --git a/src/core/__tests__/ReactMultiChild-test.js b/src/core/__tests__/ReactMultiChild-test.js
index b52ad5319a..7ddb05ae53 100644
--- a/src/core/__tests__/ReactMultiChild-test.js
+++ b/src/core/__tests__/ReactMultiChild-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks = require('mocks');
 
diff --git a/src/core/__tests__/ReactMultiChildReconcile-test.js b/src/core/__tests__/ReactMultiChildReconcile-test.js
index a56075fc5e..550ea254be 100644
--- a/src/core/__tests__/ReactMultiChildReconcile-test.js
+++ b/src/core/__tests__/ReactMultiChildReconcile-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules');
 
diff --git a/src/core/__tests__/ReactMultiChildText-test.js b/src/core/__tests__/ReactMultiChildText-test.js
index 7cdce88b7a..948cec3df4 100644
--- a/src/core/__tests__/ReactMultiChildText-test.js
+++ b/src/core/__tests__/ReactMultiChildText-test.js
@@ -11,7 +11,7 @@
 
 /*jslint evil: true */
 
-"use strict";
+'use strict';
 
 require('mock-modules');
 
diff --git a/src/core/__tests__/ReactStateSetters-test.js b/src/core/__tests__/ReactStateSetters-test.js
index 0b2d651710..51731085b4 100644
--- a/src/core/__tests__/ReactStateSetters-test.js
+++ b/src/core/__tests__/ReactStateSetters-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactStateSetters = require('ReactStateSetters');
diff --git a/src/core/__tests__/ReactUpdates-test.js b/src/core/__tests__/ReactUpdates-test.js
index 052d61e25d..e9334aaa47 100644
--- a/src/core/__tests__/ReactUpdates-test.js
+++ b/src/core/__tests__/ReactUpdates-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTestUtils;
diff --git a/src/core/__tests__/refs-destruction-test.js b/src/core/__tests__/refs-destruction-test.js
index fc1ff60108..b5b68b43ad 100644
--- a/src/core/__tests__/refs-destruction-test.js
+++ b/src/core/__tests__/refs-destruction-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactTestUtils = require('ReactTestUtils');
diff --git a/src/core/__tests__/refs-test.js b/src/core/__tests__/refs-test.js
index 6c7388af49..68f6579db9 100644
--- a/src/core/__tests__/refs-test.js
+++ b/src/core/__tests__/refs-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React = require('React');
 var ReactTestUtils = require('ReactTestUtils');
diff --git a/src/core/instantiateReactComponent.js b/src/core/instantiateReactComponent.js
index 36fef60f55..bc524836b9 100644
--- a/src/core/instantiateReactComponent.js
+++ b/src/core/instantiateReactComponent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ReactCompositeComponent = require('ReactCompositeComponent');
 var ReactEmptyComponent = require('ReactEmptyComponent');
diff --git a/src/core/shouldUpdateReactComponent.js b/src/core/shouldUpdateReactComponent.js
index 42ed113a4a..0bfd40ef21 100644
--- a/src/core/shouldUpdateReactComponent.js
+++ b/src/core/shouldUpdateReactComponent.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var monitorCodeUse = require('monitorCodeUse');
 
@@ -39,19 +39,22 @@ function shouldUpdateReactComponent(prevElement, nextElement) {
         var prevName = null;
         var nextName = null;
         var nextDisplayName = null;
-        if(__DEV__) {
+        if (__DEV__) {
           if (!ownersMatch) {
             if (prevElement._owner != null &&
                 prevElement._owner.getPublicInstance() != null &&
                 prevElement._owner.getPublicInstance().constructor != null) {
-              prevName = prevElement._owner.getPublicInstance().constructor.displayName;
+              prevName =
+                prevElement._owner.getPublicInstance().constructor.displayName;
             }
             if (nextElement._owner != null &&
                 nextElement._owner.getPublicInstance() != null &&
                 nextElement._owner.getPublicInstance().constructor != null) {
-              nextName = nextElement._owner.getPublicInstance().constructor.displayName;
+              nextName =
+                nextElement._owner.getPublicInstance().constructor.displayName;
             }
-            if(nextElement.type != null && nextElement.type.displayName != null) {
+            if (nextElement.type != null &&
+                nextElement.type.displayName != null) {
               nextDisplayName = nextElement.type.displayName;
             }
             monitorCodeUse(
diff --git a/src/event/EventConstants.js b/src/event/EventConstants.js
index b3bf14c7bc..1735086492 100644
--- a/src/event/EventConstants.js
+++ b/src/event/EventConstants.js
@@ -9,7 +9,7 @@
  * @providesModule EventConstants
  */
 
-"use strict";
+'use strict';
 
 var keyMirror = require('keyMirror');
 
diff --git a/src/event/EventPluginHub.js b/src/event/EventPluginHub.js
index ae77acf83a..e49c122ab3 100644
--- a/src/event/EventPluginHub.js
+++ b/src/event/EventPluginHub.js
@@ -9,7 +9,7 @@
  * @providesModule EventPluginHub
  */
 
-"use strict";
+'use strict';
 
 var EventPluginRegistry = require('EventPluginRegistry');
 var EventPluginUtils = require('EventPluginUtils');
@@ -58,12 +58,14 @@ var executeDispatchesAndRelease = function(event) {
 var InstanceHandle = null;
 
 function validateInstanceHandle() {
-  var invalid = !InstanceHandle||
-    !InstanceHandle.traverseTwoPhase ||
-    !InstanceHandle.traverseEnterLeave;
-  if (invalid) {
-    throw new Error('InstanceHandle not injected before use!');
-  }
+  var valid =
+    InstanceHandle &&
+    InstanceHandle.traverseTwoPhase &&
+    InstanceHandle.traverseEnterLeave;
+  invariant(
+    valid,
+    'InstanceHandle not injected before use!'
+  );
 }
 
 /**
diff --git a/src/event/EventPluginRegistry.js b/src/event/EventPluginRegistry.js
index faa774115d..c4f553cdd0 100644
--- a/src/event/EventPluginRegistry.js
+++ b/src/event/EventPluginRegistry.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/event/EventPluginUtils.js b/src/event/EventPluginUtils.js
index f0566a85ec..bc4ec7ad42 100644
--- a/src/event/EventPluginUtils.js
+++ b/src/event/EventPluginUtils.js
@@ -9,7 +9,7 @@
  * @providesModule EventPluginUtils
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 
diff --git a/src/event/EventPropagators.js b/src/event/EventPropagators.js
index f37614a1f0..19994fdfb0 100644
--- a/src/event/EventPropagators.js
+++ b/src/event/EventPropagators.js
@@ -9,7 +9,7 @@
  * @providesModule EventPropagators
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginHub = require('EventPluginHub');
diff --git a/src/event/__tests__/EventPluginHub-test.js b/src/event/__tests__/EventPluginHub-test.js
index 96cd63292a..f28ba0cab6 100644
--- a/src/event/__tests__/EventPluginHub-test.js
+++ b/src/event/__tests__/EventPluginHub-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules')
   .dontMock('EventPluginHub')
diff --git a/src/event/__tests__/EventPluginRegistry-test.js b/src/event/__tests__/EventPluginRegistry-test.js
index 8455e8f905..1dd16fc3df 100644
--- a/src/event/__tests__/EventPluginRegistry-test.js
+++ b/src/event/__tests__/EventPluginRegistry-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 
diff --git a/src/modern/class/ReactComponentBase.js b/src/modern/class/ReactComponentBase.js
index 719adb6768..68a60bfc78 100644
--- a/src/modern/class/ReactComponentBase.js
+++ b/src/modern/class/ReactComponentBase.js
@@ -9,11 +9,10 @@
  * @providesModule ReactComponentBase
  */
 
-"use strict";
+'use strict';
 
 var ReactInstanceMap = require('ReactInstanceMap');
 
-var assign = require('Object.assign');
 var invariant = require('invariant');
 var warning = require('warning');
 
@@ -57,7 +56,7 @@ ReactComponentBase.prototype.setState = function(partialState, callback) {
   var internalInstance = ReactInstanceMap.get(this);
   invariant(
     internalInstance,
-    'setState(...): Can only update a mounted or mounting component. ' + 
+    'setState(...): Can only update a mounted or mounting component. ' +
     'This usually means you called setState() on an unmounted ' +
     'component.'
   );
diff --git a/src/modern/class/__tests__/ReactES6Class-test.js b/src/modern/class/__tests__/ReactES6Class-test.js
index b64e198864..b604d18550 100644
--- a/src/modern/class/__tests__/ReactES6Class-test.js
+++ b/src/modern/class/__tests__/ReactES6Class-test.js
@@ -9,9 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
-
-var mocks = require('mocks');
+'use strict';
 
 var React;
 
diff --git a/src/modern/element/__tests__/ReactJSXElement-test.js b/src/modern/element/__tests__/ReactJSXElement-test.js
index 8044a7be69..0fc6851dea 100644
--- a/src/modern/element/__tests__/ReactJSXElement-test.js
+++ b/src/modern/element/__tests__/ReactJSXElement-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var mocks;
 
diff --git a/src/modern/element/__tests__/ReactJSXElementValidator-test.js b/src/modern/element/__tests__/ReactJSXElementValidator-test.js
index 76abef884a..5ed0823dc7 100644
--- a/src/modern/element/__tests__/ReactJSXElementValidator-test.js
+++ b/src/modern/element/__tests__/ReactJSXElementValidator-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 // TODO: All these warnings should become static errors using Flow instead
 // of dynamic errors when using JSX with Flow.
diff --git a/src/modern/types/__tests__/ReactFlowPropTypes-test.js b/src/modern/types/__tests__/ReactFlowPropTypes-test.js
index 6313667651..93b029a6db 100644
--- a/src/modern/types/__tests__/ReactFlowPropTypes-test.js
+++ b/src/modern/types/__tests__/ReactFlowPropTypes-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('ReactFlowPropTypes', function() {
 
diff --git a/src/modern/types/__tests__/ReactTypeScriptPropTypes-test.js b/src/modern/types/__tests__/ReactTypeScriptPropTypes-test.js
index 27aca01fa1..846e201f04 100644
--- a/src/modern/types/__tests__/ReactTypeScriptPropTypes-test.js
+++ b/src/modern/types/__tests__/ReactTypeScriptPropTypes-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('ReactTypeScriptPropTypes', function() {
 
diff --git a/src/stubs/Object.assign.js b/src/stubs/Object.assign.js
index 4fdef7c1b3..8035fae90a 100644
--- a/src/stubs/Object.assign.js
+++ b/src/stubs/Object.assign.js
@@ -11,7 +11,7 @@
 
 // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.assign
 
-"use strict";
+'use strict';
 
 function assign(target, sources) {
   if (target == null) {
diff --git a/src/test/ReactDefaultPerf.js b/src/test/ReactDefaultPerf.js
index cbc5d0150a..8c8fcb4dea 100644
--- a/src/test/ReactDefaultPerf.js
+++ b/src/test/ReactDefaultPerf.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var DOMProperty = require('DOMProperty');
 var ReactDefaultPerfAnalysis = require('ReactDefaultPerfAnalysis');
diff --git a/src/test/ReactPerf.js b/src/test/ReactPerf.js
index ceec3f8678..1bf4861889 100644
--- a/src/test/ReactPerf.js
+++ b/src/test/ReactPerf.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * ReactPerf is a general AOP system designed to measure performance. This
diff --git a/src/test/ReactTestUtils.js b/src/test/ReactTestUtils.js
index 4b9f997180..da8968085b 100644
--- a/src/test/ReactTestUtils.js
+++ b/src/test/ReactTestUtils.js
@@ -9,7 +9,7 @@
  * @providesModule ReactTestUtils
  */
 
-"use strict";
+'use strict';
 
 var EventConstants = require('EventConstants');
 var EventPluginHub = require('EventPluginHub');
diff --git a/src/test/__tests__/ReactTestUtils-test.js b/src/test/__tests__/ReactTestUtils-test.js
index 41a0877373..7f16edc43c 100644
--- a/src/test/__tests__/ReactTestUtils-test.js
+++ b/src/test/__tests__/ReactTestUtils-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTestUtils;
diff --git a/src/test/__tests__/reactComponentExpect-test.js b/src/test/__tests__/reactComponentExpect-test.js
index c12b451bb1..bb6f9fb87d 100644
--- a/src/test/__tests__/reactComponentExpect-test.js
+++ b/src/test/__tests__/reactComponentExpect-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var React;
 var ReactTestUtils;
diff --git a/src/test/getTestDocument.js b/src/test/getTestDocument.js
index 157afc865f..075174de61 100644
--- a/src/test/getTestDocument.js
+++ b/src/test/getTestDocument.js
@@ -9,7 +9,7 @@
  * @providesModule getTestDocument
  */
 
-"use strict";
+'use strict';
 
 function getTestDocument(markup) {
   var iframe = document.createElement('iframe');
diff --git a/src/test/reactComponentExpect.js b/src/test/reactComponentExpect.js
index 2f2df87f25..741eea501a 100644
--- a/src/test/reactComponentExpect.js
+++ b/src/test/reactComponentExpect.js
@@ -10,7 +10,7 @@
  * @nolint
  */
 
-"use strict";
+'use strict';
 
 var ReactInstanceMap = require('ReactInstanceMap');
 var ReactTestUtils = require('ReactTestUtils');
diff --git a/src/test/worker.js b/src/test/worker.js
index 10691fda0b..1805e33b02 100644
--- a/src/test/worker.js
+++ b/src/test/worker.js
@@ -1,5 +1,5 @@
 /* jshint worker: true */
-"use strict";
+'use strict';
 
 if (typeof console == 'undefined') {
   this.console = {
diff --git a/src/utils/CallbackQueue.js b/src/utils/CallbackQueue.js
index be51b7f57b..8268312993 100644
--- a/src/utils/CallbackQueue.js
+++ b/src/utils/CallbackQueue.js
@@ -9,7 +9,7 @@
  * @providesModule CallbackQueue
  */
 
-"use strict";
+'use strict';
 
 var PooledClass = require('PooledClass');
 
@@ -60,7 +60,7 @@ assign(CallbackQueue.prototype, {
     if (callbacks) {
       invariant(
         callbacks.length === contexts.length,
-        "Mismatched list of contexts in callback queue"
+        'Mismatched list of contexts in callback queue'
       );
       this._callbacks = null;
       this._contexts = null;
diff --git a/src/utils/OrderedMap.js b/src/utils/OrderedMap.js
index 7e0c00b1af..54da66bb32 100644
--- a/src/utils/OrderedMap.js
+++ b/src/utils/OrderedMap.js
@@ -9,7 +9,7 @@
  * @providesModule OrderedMap
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 var invariant = require('invariant');
@@ -29,7 +29,7 @@ var PREFIX = 'key:';
  */
 function extractObjectFromArray(arr, keyExtractor) {
   var normalizedObj = {};
-  for (var i=0; i < arr.length; i++) {
+  for (var i = 0; i < arr.length; i++) {
     var item = arr[i];
     var key = keyExtractor(item);
     assertValidPublicKey(key);
diff --git a/src/utils/PooledClass.js b/src/utils/PooledClass.js
index 959e47abb0..0acab61257 100644
--- a/src/utils/PooledClass.js
+++ b/src/utils/PooledClass.js
@@ -9,7 +9,7 @@
  * @providesModule PooledClass
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/utils/ReactChildren.js b/src/utils/ReactChildren.js
index e8e89bb513..097c659c9d 100644
--- a/src/utils/ReactChildren.js
+++ b/src/utils/ReactChildren.js
@@ -9,7 +9,7 @@
  * @providesModule ReactChildren
  */
 
-"use strict";
+'use strict';
 
 var PooledClass = require('PooledClass');
 
diff --git a/src/utils/Transaction.js b/src/utils/Transaction.js
index 8ba3e825c2..3ba59c8afd 100644
--- a/src/utils/Transaction.js
+++ b/src/utils/Transaction.js
@@ -9,7 +9,7 @@
  * @providesModule Transaction
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
@@ -203,8 +203,8 @@ var Mixin = {
         // close -- if it's still set to true in the finally block, it means
         // wrapper.close threw.
         errorThrown = true;
-        if (initData !== Transaction.OBSERVED_ERROR) {
-          wrapper.close && wrapper.close.call(this, initData);
+        if (initData !== Transaction.OBSERVED_ERROR && wrapper.close) {
+          wrapper.close.call(this, initData);
         }
         errorThrown = false;
       } finally {
diff --git a/src/utils/__tests__/OrderedMap-test.js b/src/utils/__tests__/OrderedMap-test.js
index e1bffba73a..f44034bf9a 100644
--- a/src/utils/__tests__/OrderedMap-test.js
+++ b/src/utils/__tests__/OrderedMap-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var OrderedMap;
 
diff --git a/src/utils/__tests__/PooledClass-test.js b/src/utils/__tests__/PooledClass-test.js
index d68fc01494..e60e50cd87 100644
--- a/src/utils/__tests__/PooledClass-test.js
+++ b/src/utils/__tests__/PooledClass-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var PooledClass;
 var PoolableClass;
diff --git a/src/utils/__tests__/ReactChildren-test.js b/src/utils/__tests__/ReactChildren-test.js
index 859d6d220f..cb447dd884 100644
--- a/src/utils/__tests__/ReactChildren-test.js
+++ b/src/utils/__tests__/ReactChildren-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('ReactChildren', function() {
   var ReactChildren;
diff --git a/src/utils/__tests__/Transaction-test.js b/src/utils/__tests__/Transaction-test.js
index ad9069f88c..90f347b8d3 100644
--- a/src/utils/__tests__/Transaction-test.js
+++ b/src/utils/__tests__/Transaction-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 
diff --git a/src/utils/__tests__/accumulateInto-test.js b/src/utils/__tests__/accumulateInto-test.js
index 7df6ad0c3f..b7d86c10c4 100644
--- a/src/utils/__tests__/accumulateInto-test.js
+++ b/src/utils/__tests__/accumulateInto-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules')
   .dontMock('accumulateInto');
diff --git a/src/utils/__tests__/cloneWithProps-test.js b/src/utils/__tests__/cloneWithProps-test.js
index 93fdfc5b26..e4712ea00b 100644
--- a/src/utils/__tests__/cloneWithProps-test.js
+++ b/src/utils/__tests__/cloneWithProps-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules')
   .dontMock('cloneWithProps')
diff --git a/src/utils/__tests__/escapeTextForBrowser-test.js b/src/utils/__tests__/escapeTextForBrowser-test.js
index a7b37bd699..138e72b0f1 100644
--- a/src/utils/__tests__/escapeTextForBrowser-test.js
+++ b/src/utils/__tests__/escapeTextForBrowser-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('escapeTextForBrowser', function() {
 
diff --git a/src/utils/__tests__/joinClasses-test.js b/src/utils/__tests__/joinClasses-test.js
index 75c64a6618..0dc5aa2704 100644
--- a/src/utils/__tests__/joinClasses-test.js
+++ b/src/utils/__tests__/joinClasses-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules').dontMock('joinClasses');
 
diff --git a/src/utils/__tests__/keyMirror-test.js b/src/utils/__tests__/keyMirror-test.js
index 8d7a5dddad..2c9de29bac 100644
--- a/src/utils/__tests__/keyMirror-test.js
+++ b/src/utils/__tests__/keyMirror-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 require('mock-modules').dontMock('keyMirror');
 
diff --git a/src/utils/__tests__/memoizeStringOnly-test.js b/src/utils/__tests__/memoizeStringOnly-test.js
index 5561ad40ec..e7a7e568b2 100644
--- a/src/utils/__tests__/memoizeStringOnly-test.js
+++ b/src/utils/__tests__/memoizeStringOnly-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('memoizeStringOnly', function() {
   var memoizeStringOnly;
diff --git a/src/utils/__tests__/onlyChild-test.js b/src/utils/__tests__/onlyChild-test.js
index 12eba1e186..2ba5e70924 100644
--- a/src/utils/__tests__/onlyChild-test.js
+++ b/src/utils/__tests__/onlyChild-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('onlyChild', function() {
 
diff --git a/src/utils/__tests__/sliceChildren-test.js b/src/utils/__tests__/sliceChildren-test.js
index 5bd0b600ad..b45417bb69 100644
--- a/src/utils/__tests__/sliceChildren-test.js
+++ b/src/utils/__tests__/sliceChildren-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('sliceChildren', function() {
 
diff --git a/src/utils/__tests__/traverseAllChildren-test.js b/src/utils/__tests__/traverseAllChildren-test.js
index b14ff2bdfc..1ff047d2e4 100644
--- a/src/utils/__tests__/traverseAllChildren-test.js
+++ b/src/utils/__tests__/traverseAllChildren-test.js
@@ -9,7 +9,7 @@
  * @emails react-core
  */
 
-"use strict";
+'use strict';
 
 describe('traverseAllChildren', function() {
   var traverseAllChildren;
diff --git a/src/utils/accumulate.js b/src/utils/accumulate.js
index 966efa3a7a..d0e98c7775 100644
--- a/src/utils/accumulate.js
+++ b/src/utils/accumulate.js
@@ -9,7 +9,7 @@
  * @providesModule accumulate
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/utils/accumulateInto.js b/src/utils/accumulateInto.js
index 10b1bdc20f..885c8ef658 100644
--- a/src/utils/accumulateInto.js
+++ b/src/utils/accumulateInto.js
@@ -9,7 +9,7 @@
  * @providesModule accumulateInto
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/utils/adler32.js b/src/utils/adler32.js
index 5de4549ad6..4e546c5633 100644
--- a/src/utils/adler32.js
+++ b/src/utils/adler32.js
@@ -11,7 +11,7 @@
 
 /* jslint bitwise:true */
 
-"use strict";
+'use strict';
 
 var MOD = 65521;
 
diff --git a/src/utils/cloneWithProps.js b/src/utils/cloneWithProps.js
index d7aa2a0c18..b0dd722469 100644
--- a/src/utils/cloneWithProps.js
+++ b/src/utils/cloneWithProps.js
@@ -10,7 +10,7 @@
  * @providesModule cloneWithProps
  */
 
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactPropTransferer = require('ReactPropTransferer');
diff --git a/src/utils/deprecated.js b/src/utils/deprecated.js
index 0e07e222ef..f976789f36 100644
--- a/src/utils/deprecated.js
+++ b/src/utils/deprecated.js
@@ -9,7 +9,7 @@
  * @providesModule deprecated
  */
 
-"use strict";
+'use strict';
 
 var assign = require('Object.assign');
 var warning = require('warning');
diff --git a/src/utils/escapeTextForBrowser.js b/src/utils/escapeTextForBrowser.js
index e2258a478c..8f8b435b39 100644
--- a/src/utils/escapeTextForBrowser.js
+++ b/src/utils/escapeTextForBrowser.js
@@ -10,14 +10,14 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var ESCAPE_LOOKUP = {
-  "&": "&amp;",
-  ">": "&gt;",
-  "<": "&lt;",
-  "\"": "&quot;",
-  "'": "&#x27;"
+  '&': '&amp;',
+  '>': '&gt;',
+  '<': '&lt;',
+  '"': '&quot;',
+  '\'': '&#x27;'
 };
 
 var ESCAPE_REGEX = /[&><"']/g;
diff --git a/src/utils/flattenChildren.js b/src/utils/flattenChildren.js
index 79f48af11b..f1af785883 100644
--- a/src/utils/flattenChildren.js
+++ b/src/utils/flattenChildren.js
@@ -9,7 +9,7 @@
  * @providesModule flattenChildren
  */
 
-"use strict";
+'use strict';
 
 var traverseAllChildren = require('traverseAllChildren');
 var warning = require('warning');
diff --git a/src/utils/forEachAccumulated.js b/src/utils/forEachAccumulated.js
index 5d04bc60e6..92e373398a 100644
--- a/src/utils/forEachAccumulated.js
+++ b/src/utils/forEachAccumulated.js
@@ -9,7 +9,7 @@
  * @providesModule forEachAccumulated
  */
 
-"use strict";
+'use strict';
 
 /**
  * @param {array} an "accumulation" of items which is either an Array or
diff --git a/src/utils/getIteratorFn.js b/src/utils/getIteratorFn.js
index 9fa8bbedf8..f454f83a66 100644
--- a/src/utils/getIteratorFn.js
+++ b/src/utils/getIteratorFn.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /* global Symbol */
 var ITERATOR_SYMBOL = typeof Symbol === 'function' && Symbol.iterator;
diff --git a/src/utils/isTextInputElement.js b/src/utils/isTextInputElement.js
index 04eb096169..76af893af9 100644
--- a/src/utils/isTextInputElement.js
+++ b/src/utils/isTextInputElement.js
@@ -9,7 +9,7 @@
  * @providesModule isTextInputElement
  */
 
-"use strict";
+'use strict';
 
 /**
  * @see http://www.whatwg.org/specs/web-apps/current-work/multipage/the-input-element.html#input-type-attr-summary
diff --git a/src/utils/joinClasses.js b/src/utils/joinClasses.js
index f1a98b0286..1897cd28ed 100644
--- a/src/utils/joinClasses.js
+++ b/src/utils/joinClasses.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * Combines multiple className strings into one.
diff --git a/src/utils/keyMirror.js b/src/utils/keyMirror.js
index 0e0c614795..e20917661c 100644
--- a/src/utils/keyMirror.js
+++ b/src/utils/keyMirror.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 var invariant = require('invariant');
 
diff --git a/src/utils/memoizeStringOnly.js b/src/utils/memoizeStringOnly.js
index 0f3e9b3c2c..7777f0e877 100644
--- a/src/utils/memoizeStringOnly.js
+++ b/src/utils/memoizeStringOnly.js
@@ -10,7 +10,7 @@
  * @typechecks static-only
  */
 
-"use strict";
+'use strict';
 
 /**
  * Memoizes the return value of a function that accepts one string argument.
@@ -21,11 +21,10 @@
 function memoizeStringOnly(callback) {
   var cache = {};
   return function(string) {
-    if (cache.hasOwnProperty(string)) {
-      return cache[string];
-    } else {
-      return cache[string] = callback.call(this, string);
+    if (!cache.hasOwnProperty(string)) {
+      cache[string] = callback.call(this, string);
     }
+    return cache[string];
   };
 }
 
diff --git a/src/utils/onlyChild.js b/src/utils/onlyChild.js
index 51467c1c27..14d9aff4ff 100644
--- a/src/utils/onlyChild.js
+++ b/src/utils/onlyChild.js
@@ -8,7 +8,7 @@
  *
  * @providesModule onlyChild
  */
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 
diff --git a/src/utils/shallowEqual.js b/src/utils/shallowEqual.js
index c52a37d57d..e5e8542b9c 100644
--- a/src/utils/shallowEqual.js
+++ b/src/utils/shallowEqual.js
@@ -9,7 +9,7 @@
  * @providesModule shallowEqual
  */
 
-"use strict";
+'use strict';
 
 /**
  * Performs equality by iterating through keys on an object and returning
diff --git a/src/utils/sliceChildren.js b/src/utils/sliceChildren.js
index 91b19eabbb..e721ee9f41 100644
--- a/src/utils/sliceChildren.js
+++ b/src/utils/sliceChildren.js
@@ -9,7 +9,7 @@
  * @providesModule sliceChildren
  */
 
-"use strict";
+'use strict';
 
 var flattenChildren = require('flattenChildren');
 
diff --git a/src/utils/traverseAllChildren.js b/src/utils/traverseAllChildren.js
index 90295ea4b5..a54acb58c7 100644
--- a/src/utils/traverseAllChildren.js
+++ b/src/utils/traverseAllChildren.js
@@ -9,7 +9,7 @@
  * @providesModule traverseAllChildren
  */
 
-"use strict";
+'use strict';
 
 var ReactElement = require('ReactElement');
 var ReactInstanceHandles = require('ReactInstanceHandles');