From 096360db0303f7582eae80331ee4a54762f3b022 Mon Sep 17 00:00:00 2001
From: Sebastian Markbage <sema@fb.com>
Date: Wed, 8 Oct 2014 11:32:40 -0700
Subject: [PATCH] Use Object.assign instead of merge, mergeInto, mixInto and
 copyProperties

This makes it easier to contribute without having to learn a bunch of
slightly different helpers and remember their slightly different
signatures and semantics.

We'll probably start using ES7 spread properties instead of merge in the
future when at least one more transpiler supports it.
---
 .../transitions/ReactCSSTransitionGroup.js    |  4 +--
 .../transitions/ReactTransitionGroup.js       |  3 +-
 src/addons/update.js                          |  5 ++-
 src/browser/ReactBrowserEventEmitter.js       |  3 +-
 src/browser/ReactPutListenerQueue.js          |  4 +--
 src/browser/ReactReconcileTransaction.js      |  5 +--
 src/browser/ReactTextComponent.js             |  4 +--
 .../server/ReactServerRenderingTransaction.js |  8 +++--
 src/browser/syntheticEvents/SyntheticEvent.js |  8 ++---
 src/browser/ui/ReactDOMComponent.js           | 17 +++++-----
 src/browser/ui/ReactEventListener.js          |  3 +-
 .../ui/__tests__/ReactDOMComponent-test.js    | 13 +++----
 .../ui/dom/components/ReactDOMInput.js        |  3 +-
 .../ui/dom/components/ReactDOMSelect.js       |  4 +--
 .../ui/dom/components/ReactDOMTextarea.js     |  3 +-
 src/core/ReactComponent.js                    |  5 ++-
 src/core/ReactCompositeComponent.js           | 34 ++++++++++++-------
 src/core/ReactContext.js                      |  4 +--
 src/core/ReactDefaultBatchingStrategy.js      | 14 ++++----
 src/core/ReactLegacyElement.js                |  2 +-
 src/core/ReactNativeComponent.js              |  3 +-
 src/core/ReactPropTransferer.js               |  5 ++-
 src/core/ReactUpdates.js                      |  6 ++--
 .../__tests__/EventPluginRegistry-test.js     |  4 +--
 src/test/ReactDefaultPerfAnalysis.js          | 16 ++++++---
 src/test/ReactTestUtils.js                    |  6 ++--
 src/test/reactComponentExpect.js              |  4 +--
 src/utils/CallbackQueue.js                    |  3 +-
 src/utils/LegacyImmutableObject.js            | 10 +++---
 src/utils/OrderedMap.js                       |  3 +-
 src/utils/__tests__/Transaction-test.js       | 14 ++++----
 src/utils/mixInto.js                          | 34 -------------------
 src/vendor/core/emptyFunction.js              |  4 +--
 src/vendor/immutable/Immutable.js             |  3 +-
 34 files changed, 103 insertions(+), 158 deletions(-)
 delete mode 100644 src/utils/mixInto.js

diff --git a/src/addons/transitions/ReactCSSTransitionGroup.js b/src/addons/transitions/ReactCSSTransitionGroup.js
index c54d9a7aeb..5b6ce5607c 100644
--- a/src/addons/transitions/ReactCSSTransitionGroup.js
+++ b/src/addons/transitions/ReactCSSTransitionGroup.js
@@ -28,8 +28,6 @@ var ReactCSSTransitionGroupChild = React.createFactory(
   require('ReactCSSTransitionGroupChild')
 );
 
-var merge = require('merge');
-
 var ReactCSSTransitionGroup = React.createClass({
   displayName: 'ReactCSSTransitionGroup',
 
@@ -63,7 +61,7 @@ var ReactCSSTransitionGroup = React.createClass({
   render: function() {
     return (
       ReactTransitionGroup(
-        merge(this.props, {childFactory: this._wrapChild})
+        Object.assign({}, this.props, {childFactory: this._wrapChild})
       )
     );
   }
diff --git a/src/addons/transitions/ReactTransitionGroup.js b/src/addons/transitions/ReactTransitionGroup.js
index 174d389676..1203abb703 100644
--- a/src/addons/transitions/ReactTransitionGroup.js
+++ b/src/addons/transitions/ReactTransitionGroup.js
@@ -23,7 +23,6 @@ var ReactTransitionChildMapping = require('ReactTransitionChildMapping');
 
 var cloneWithProps = require('cloneWithProps');
 var emptyFunction = require('emptyFunction');
-var merge = require('merge');
 
 var ReactTransitionGroup = React.createClass({
   displayName: 'ReactTransitionGroup',
@@ -159,7 +158,7 @@ var ReactTransitionGroup = React.createClass({
       // This entered again before it fully left. Add it again.
       this.performEnter(key);
     } else {
-      var newChildren = merge(this.state.children);
+      var newChildren = Object.assign({}, this.state.children);
       delete newChildren[key];
       this.setState({children: newChildren});
     }
diff --git a/src/addons/update.js b/src/addons/update.js
index 43ec8dd53f..c55f4b13dd 100644
--- a/src/addons/update.js
+++ b/src/addons/update.js
@@ -18,7 +18,6 @@
 
 "use strict";
 
-var copyProperties = require('copyProperties');
 var keyOf = require('keyOf');
 var invariant = require('invariant');
 
@@ -26,7 +25,7 @@ function shallowCopy(x) {
   if (Array.isArray(x)) {
     return x.concat();
   } else if (x && typeof x === 'object') {
-    return copyProperties(new x.constructor(), x);
+    return Object.assign(new x.constructor(), x);
   } else {
     return x;
   }
@@ -106,7 +105,7 @@ function update(value, spec) {
       COMMAND_MERGE,
       nextValue
     );
-    copyProperties(nextValue, spec[COMMAND_MERGE]);
+    Object.assign(nextValue, spec[COMMAND_MERGE]);
   }
 
   if (spec.hasOwnProperty(COMMAND_PUSH)) {
diff --git a/src/browser/ReactBrowserEventEmitter.js b/src/browser/ReactBrowserEventEmitter.js
index 677b076986..62d65347b7 100644
--- a/src/browser/ReactBrowserEventEmitter.js
+++ b/src/browser/ReactBrowserEventEmitter.js
@@ -26,7 +26,6 @@ var ReactEventEmitterMixin = require('ReactEventEmitterMixin');
 var ViewportMetrics = require('ViewportMetrics');
 
 var isEventSupported = require('isEventSupported');
-var merge = require('merge');
 
 /**
  * Summary of `ReactBrowserEventEmitter` event handling:
@@ -155,7 +154,7 @@ function getListeningForDocument(mountAt) {
  *
  * @internal
  */
-var ReactBrowserEventEmitter = merge(ReactEventEmitterMixin, {
+var ReactBrowserEventEmitter = Object.assign({}, ReactEventEmitterMixin, {
 
   /**
    * Injectable event backend
diff --git a/src/browser/ReactPutListenerQueue.js b/src/browser/ReactPutListenerQueue.js
index 0e2500e499..31256aaaaf 100644
--- a/src/browser/ReactPutListenerQueue.js
+++ b/src/browser/ReactPutListenerQueue.js
@@ -21,13 +21,11 @@
 var PooledClass = require('PooledClass');
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
 
-var mixInto = require('mixInto');
-
 function ReactPutListenerQueue() {
   this.listenersToPut = [];
 }
 
-mixInto(ReactPutListenerQueue, {
+Object.assign(ReactPutListenerQueue.prototype, {
   enqueuePutListener: function(rootNodeID, propKey, propValue) {
     this.listenersToPut.push({
       rootNodeID: rootNodeID,
diff --git a/src/browser/ReactReconcileTransaction.js b/src/browser/ReactReconcileTransaction.js
index e4ac1ffa02..42c88cbca2 100644
--- a/src/browser/ReactReconcileTransaction.js
+++ b/src/browser/ReactReconcileTransaction.js
@@ -26,8 +26,6 @@ var ReactInputSelection = require('ReactInputSelection');
 var ReactPutListenerQueue = require('ReactPutListenerQueue');
 var Transaction = require('Transaction');
 
-var mixInto = require('mixInto');
-
 /**
  * Ensures that, when possible, the selection range (currently selected text
  * input) is not disturbed by performing the transaction.
@@ -174,8 +172,7 @@ var Mixin = {
 };
 
 
-mixInto(ReactReconcileTransaction, Transaction.Mixin);
-mixInto(ReactReconcileTransaction, Mixin);
+Object.assign(ReactReconcileTransaction.prototype, Transaction.Mixin, Mixin);
 
 PooledClass.addPoolingTo(ReactReconcileTransaction);
 
diff --git a/src/browser/ReactTextComponent.js b/src/browser/ReactTextComponent.js
index 25cdd6e1bf..aa2819fff6 100644
--- a/src/browser/ReactTextComponent.js
+++ b/src/browser/ReactTextComponent.js
@@ -25,7 +25,6 @@ var ReactComponent = require('ReactComponent');
 var ReactElement = require('ReactElement');
 
 var escapeTextForBrowser = require('escapeTextForBrowser');
-var mixInto = require('mixInto');
 
 /**
  * Text nodes violate a couple assumptions that React makes about components:
@@ -46,8 +45,7 @@ var ReactTextComponent = function(props) {
   // This constructor and it's argument is currently used by mocks.
 };
 
-mixInto(ReactTextComponent, ReactComponent.Mixin);
-mixInto(ReactTextComponent, {
+Object.assign(ReactTextComponent.prototype, ReactComponent.Mixin, {
 
   /**
    * Creates the markup for this text node. This node is not intended to have
diff --git a/src/browser/server/ReactServerRenderingTransaction.js b/src/browser/server/ReactServerRenderingTransaction.js
index 2251f82f96..7b7d8f86b6 100644
--- a/src/browser/server/ReactServerRenderingTransaction.js
+++ b/src/browser/server/ReactServerRenderingTransaction.js
@@ -25,7 +25,6 @@ var ReactPutListenerQueue = require('ReactPutListenerQueue');
 var Transaction = require('Transaction');
 
 var emptyFunction = require('emptyFunction');
-var mixInto = require('mixInto');
 
 /**
  * Provides a `CallbackQueue` queue for collecting `onDOMReady` callbacks
@@ -107,8 +106,11 @@ var Mixin = {
 };
 
 
-mixInto(ReactServerRenderingTransaction, Transaction.Mixin);
-mixInto(ReactServerRenderingTransaction, Mixin);
+Object.assign(
+  ReactServerRenderingTransaction.prototype,
+  Transaction.Mixin,
+  Mixin
+);
 
 PooledClass.addPoolingTo(ReactServerRenderingTransaction);
 
diff --git a/src/browser/syntheticEvents/SyntheticEvent.js b/src/browser/syntheticEvents/SyntheticEvent.js
index f6012d59cf..ae3fb6c54b 100644
--- a/src/browser/syntheticEvents/SyntheticEvent.js
+++ b/src/browser/syntheticEvents/SyntheticEvent.js
@@ -23,8 +23,6 @@ var PooledClass = require('PooledClass');
 
 var emptyFunction = require('emptyFunction');
 var getEventTarget = require('getEventTarget');
-var merge = require('merge');
-var mergeInto = require('mergeInto');
 
 /**
  * @interface Event
@@ -91,7 +89,7 @@ function SyntheticEvent(dispatchConfig, dispatchMarker, nativeEvent) {
   this.isPropagationStopped = emptyFunction.thatReturnsFalse;
 }
 
-mergeInto(SyntheticEvent.prototype, {
+Object.assign(SyntheticEvent.prototype, {
 
   preventDefault: function() {
     this.defaultPrevented = true;
@@ -149,11 +147,11 @@ SyntheticEvent.augmentClass = function(Class, Interface) {
   var Super = this;
 
   var prototype = Object.create(Super.prototype);
-  mergeInto(prototype, Class.prototype);
+  Object.assign(prototype, Class.prototype);
   Class.prototype = prototype;
   Class.prototype.constructor = Class;
 
-  Class.Interface = merge(Super.Interface, Interface);
+  Class.Interface = Object.assign({}, Super.Interface, Interface);
   Class.augmentClass = Super.augmentClass;
 
   PooledClass.addPoolingTo(Class, PooledClass.threeArgumentPooler);
diff --git a/src/browser/ui/ReactDOMComponent.js b/src/browser/ui/ReactDOMComponent.js
index cbbe776d3d..a7536c71c7 100644
--- a/src/browser/ui/ReactDOMComponent.js
+++ b/src/browser/ui/ReactDOMComponent.js
@@ -33,8 +33,6 @@ var escapeTextForBrowser = require('escapeTextForBrowser');
 var invariant = require('invariant');
 var isEventSupported = require('isEventSupported');
 var keyOf = require('keyOf');
-var merge = require('merge');
-var mixInto = require('mixInto');
 var monitorCodeUse = require('monitorCodeUse');
 
 var deleteListener = ReactBrowserEventEmitter.deleteListener;
@@ -207,7 +205,7 @@ ReactDOMComponent.Mixin = {
       } else {
         if (propKey === STYLE) {
           if (propValue) {
-            propValue = props.style = merge(props.style);
+            propValue = props.style = Object.assign({}, props.style);
           }
           propValue = CSSPropertyOperations.createMarkupForStyles(propValue);
         }
@@ -356,7 +354,7 @@ ReactDOMComponent.Mixin = {
       }
       if (propKey === STYLE) {
         if (nextProp) {
-          nextProp = nextProps.style = merge(nextProp);
+          nextProp = nextProps.style = Object.assign({}, nextProp);
         }
         if (lastProp) {
           // Unset styles on `lastProp` but not on `nextProp`.
@@ -465,9 +463,12 @@ ReactDOMComponent.Mixin = {
 
 };
 
-mixInto(ReactDOMComponent, ReactComponent.Mixin);
-mixInto(ReactDOMComponent, ReactDOMComponent.Mixin);
-mixInto(ReactDOMComponent, ReactMultiChild.Mixin);
-mixInto(ReactDOMComponent, ReactBrowserComponentMixin);
+Object.assign(
+  ReactDOMComponent.prototype,
+  ReactComponent.Mixin,
+  ReactDOMComponent.Mixin,
+  ReactMultiChild.Mixin,
+  ReactBrowserComponentMixin
+);
 
 module.exports = ReactDOMComponent;
diff --git a/src/browser/ui/ReactEventListener.js b/src/browser/ui/ReactEventListener.js
index 5dc6683bb7..c032b5483e 100644
--- a/src/browser/ui/ReactEventListener.js
+++ b/src/browser/ui/ReactEventListener.js
@@ -28,7 +28,6 @@ var ReactUpdates = require('ReactUpdates');
 
 var getEventTarget = require('getEventTarget');
 var getUnboundedScrollPosition = require('getUnboundedScrollPosition');
-var mixInto = require('mixInto');
 
 /**
  * Finds the parent React component of `node`.
@@ -54,7 +53,7 @@ function TopLevelCallbackBookKeeping(topLevelType, nativeEvent) {
   this.nativeEvent = nativeEvent;
   this.ancestors = [];
 }
-mixInto(TopLevelCallbackBookKeeping, {
+Object.assign(TopLevelCallbackBookKeeping.prototype, {
   destructor: function() {
     this.topLevelType = null;
     this.nativeEvent = null;
diff --git a/src/browser/ui/__tests__/ReactDOMComponent-test.js b/src/browser/ui/__tests__/ReactDOMComponent-test.js
index 3da6798f7a..7e5274c9f7 100644
--- a/src/browser/ui/__tests__/ReactDOMComponent-test.js
+++ b/src/browser/ui/__tests__/ReactDOMComponent-test.js
@@ -224,7 +224,6 @@ describe('ReactDOMComponent', function() {
       var ReactDefaultInjection = require('ReactDefaultInjection');
       ReactDefaultInjection.inject();
 
-      var mixInto = require('mixInto');
       var ReactDOMComponent = require('ReactDOMComponent');
       var ReactReconcileTransaction = require('ReactReconcileTransaction');
 
@@ -232,7 +231,7 @@ describe('ReactDOMComponent', function() {
         this.props = initialProps || {};
         this._rootNodeID = 'test';
       };
-      mixInto(NodeStub, ReactDOMComponent.Mixin);
+      Object.assign(NodeStub.prototype, ReactDOMComponent.Mixin);
 
       genMarkup = function(props) {
         var transaction = new ReactReconcileTransaction();
@@ -275,7 +274,6 @@ describe('ReactDOMComponent', function() {
     beforeEach(function() {
       require('mock-modules').dumpCache();
 
-      var mixInto = require('mixInto');
       var ReactDOMComponent = require('ReactDOMComponent');
       var ReactReconcileTransaction = require('ReactReconcileTransaction');
 
@@ -283,7 +281,7 @@ describe('ReactDOMComponent', function() {
         this.props = initialProps || {};
         this._rootNodeID = 'test';
       };
-      mixInto(NodeStub, ReactDOMComponent.Mixin);
+      Object.assign(NodeStub.prototype, ReactDOMComponent.Mixin);
 
       genMarkup = function(props) {
         var transaction = new ReactReconcileTransaction();
@@ -312,7 +310,6 @@ describe('ReactDOMComponent', function() {
     beforeEach(function() {
       require('mock-modules').dumpCache();
 
-      var mixInto = require('mixInto');
       var ReactComponent = require('ReactComponent');
       var ReactMultiChild = require('ReactMultiChild');
       var ReactDOMComponent = require('ReactDOMComponent');
@@ -321,9 +318,9 @@ describe('ReactDOMComponent', function() {
       var StubNativeComponent = function(element) {
         ReactComponent.Mixin.construct.call(this, element);
       };
-      mixInto(StubNativeComponent, ReactComponent.Mixin);
-      mixInto(StubNativeComponent, ReactDOMComponent.Mixin);
-      mixInto(StubNativeComponent, ReactMultiChild.Mixin);
+      Object.assign(StubNativeComponent.prototype, ReactComponent.Mixin);
+      Object.assign(StubNativeComponent.prototype, ReactDOMComponent.Mixin);
+      Object.assign(StubNativeComponent.prototype, ReactMultiChild.Mixin);
 
       mountComponent = function(props) {
         var transaction = new ReactReconcileTransaction();
diff --git a/src/browser/ui/dom/components/ReactDOMInput.js b/src/browser/ui/dom/components/ReactDOMInput.js
index a653d375d6..a6fbc5c530 100644
--- a/src/browser/ui/dom/components/ReactDOMInput.js
+++ b/src/browser/ui/dom/components/ReactDOMInput.js
@@ -29,7 +29,6 @@ var ReactMount = require('ReactMount');
 var ReactUpdates = require('ReactUpdates');
 
 var invariant = require('invariant');
-var merge = require('merge');
 
 // Store a reference to the <input> `ReactDOMComponent`. TODO: use string
 var input = ReactElement.createFactory(ReactDOM.input.type);
@@ -74,7 +73,7 @@ var ReactDOMInput = ReactCompositeComponent.createClass({
 
   render: function() {
     // Clone `this.props` so we don't mutate the input.
-    var props = merge(this.props);
+    var props = Object.assign({}, this.props);
 
     props.defaultChecked = null;
     props.defaultValue = null;
diff --git a/src/browser/ui/dom/components/ReactDOMSelect.js b/src/browser/ui/dom/components/ReactDOMSelect.js
index dfd5d8d665..b385b2ba59 100644
--- a/src/browser/ui/dom/components/ReactDOMSelect.js
+++ b/src/browser/ui/dom/components/ReactDOMSelect.js
@@ -26,8 +26,6 @@ var ReactElement = require('ReactElement');
 var ReactDOM = require('ReactDOM');
 var ReactUpdates = require('ReactUpdates');
 
-var merge = require('merge');
-
 // Store a reference to the <select> `ReactDOMComponent`. TODO: use string
 var select = ReactElement.createFactory(ReactDOM.select.type);
 
@@ -138,7 +136,7 @@ var ReactDOMSelect = ReactCompositeComponent.createClass({
 
   render: function() {
     // Clone `this.props` so we don't mutate the input.
-    var props = merge(this.props);
+    var props = Object.assign({}, this.props);
 
     props.onChange = this._handleChange;
     props.value = null;
diff --git a/src/browser/ui/dom/components/ReactDOMTextarea.js b/src/browser/ui/dom/components/ReactDOMTextarea.js
index 9fab8e2b89..7fa5bd9fc3 100644
--- a/src/browser/ui/dom/components/ReactDOMTextarea.js
+++ b/src/browser/ui/dom/components/ReactDOMTextarea.js
@@ -28,7 +28,6 @@ var ReactDOM = require('ReactDOM');
 var ReactUpdates = require('ReactUpdates');
 
 var invariant = require('invariant');
-var merge = require('merge');
 
 var warning = require('warning');
 
@@ -103,7 +102,7 @@ var ReactDOMTextarea = ReactCompositeComponent.createClass({
 
   render: function() {
     // Clone `this.props` so we don't mutate the input.
-    var props = merge(this.props);
+    var props = Object.assign({}, this.props);
 
     invariant(
       props.dangerouslySetInnerHTML == null,
diff --git a/src/core/ReactComponent.js b/src/core/ReactComponent.js
index 139a67e72d..236cc3a71a 100644
--- a/src/core/ReactComponent.js
+++ b/src/core/ReactComponent.js
@@ -24,7 +24,6 @@ var ReactUpdates = require('ReactUpdates');
 
 var invariant = require('invariant');
 var keyMirror = require('keyMirror');
-var merge = require('merge');
 
 /**
  * Every React component is in one of these life cycles.
@@ -151,7 +150,7 @@ var ReactComponent = {
       // element props.
       var element = this._pendingElement || this._currentElement;
       this.replaceProps(
-        merge(element.props, partialProps),
+        Object.assign({}, element.props, partialProps),
         callback
       );
     },
@@ -200,7 +199,7 @@ var ReactComponent = {
       var element = this._pendingElement || this._currentElement;
       this._pendingElement = ReactElement.cloneAndReplaceProps(
         element,
-        merge(element.props, partialProps)
+        Object.assign({}, element.props, partialProps)
       );
       ReactUpdates.enqueueUpdate(this, callback);
     },
diff --git a/src/core/ReactCompositeComponent.js b/src/core/ReactCompositeComponent.js
index 6717399fdd..851ae42f89 100644
--- a/src/core/ReactCompositeComponent.js
+++ b/src/core/ReactCompositeComponent.js
@@ -37,8 +37,6 @@ var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 var keyMirror = require('keyMirror');
 var keyOf = require('keyOf');
-var merge = require('merge');
-var mixInto = require('mixInto');
 var monitorCodeUse = require('monitorCodeUse');
 var mapObject = require('mapObject');
 var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
@@ -349,7 +347,8 @@ var RESERVED_SPEC_KEYS = {
       childContextTypes,
       ReactPropTypeLocations.childContext
     );
-    Constructor.childContextTypes = merge(
+    Constructor.childContextTypes = Object.assign(
+      {},
       Constructor.childContextTypes,
       childContextTypes
     );
@@ -360,7 +359,11 @@ var RESERVED_SPEC_KEYS = {
       contextTypes,
       ReactPropTypeLocations.context
     );
-    Constructor.contextTypes = merge(Constructor.contextTypes, contextTypes);
+    Constructor.contextTypes = Object.assign(
+      {},
+      Constructor.contextTypes,
+      contextTypes
+    );
   },
   /**
    * Special case getDefaultProps which should move into statics but requires
@@ -382,7 +385,11 @@ var RESERVED_SPEC_KEYS = {
       propTypes,
       ReactPropTypeLocations.prop
     );
-    Constructor.propTypes = merge(Constructor.propTypes, propTypes);
+    Constructor.propTypes = Object.assign(
+      {},
+      Constructor.propTypes,
+      propTypes
+    );
   },
   statics: function(Constructor, statics) {
     mixStaticSpecIntoComponent(Constructor, statics);
@@ -462,7 +469,7 @@ function validateLifeCycleOnReplaceState(instance) {
 }
 
 /**
- * Custom version of `mixInto` which handles policy validation and reserved
+ * Mixin helper which handles policy validation and reserved
  * specification keys when building `ReactCompositeComponent` classses.
  */
 function mixSpecIntoComponent(Constructor, spec) {
@@ -866,7 +873,7 @@ var ReactCompositeComponentMixin = {
     }
     // Merge with `_pendingState` if it exists, otherwise with existing state.
     this.replaceState(
-      merge(this._pendingState || this.state, partialState),
+      Object.assign({}, this._pendingState || this.state, partialState),
       callback
     );
   },
@@ -954,7 +961,7 @@ var ReactCompositeComponentMixin = {
           name
         );
       }
-      return merge(currentContext, childContext);
+      return Object.assign({}, currentContext, childContext);
     }
     return currentContext;
   },
@@ -1332,10 +1339,13 @@ var ReactCompositeComponentMixin = {
 };
 
 var ReactCompositeComponentBase = function() {};
-mixInto(ReactCompositeComponentBase, ReactComponent.Mixin);
-mixInto(ReactCompositeComponentBase, ReactOwner.Mixin);
-mixInto(ReactCompositeComponentBase, ReactPropTransferer.Mixin);
-mixInto(ReactCompositeComponentBase, ReactCompositeComponentMixin);
+Object.assign(
+  ReactCompositeComponentBase.prototype,
+  ReactComponent.Mixin,
+  ReactOwner.Mixin,
+  ReactPropTransferer.Mixin,
+  ReactCompositeComponentMixin
+);
 
 /**
  * Module for creating composite components.
diff --git a/src/core/ReactContext.js b/src/core/ReactContext.js
index 18ce40fe3b..f7f268c53a 100644
--- a/src/core/ReactContext.js
+++ b/src/core/ReactContext.js
@@ -18,8 +18,6 @@
 
 "use strict";
 
-var merge = require('merge');
-
 /**
  * Keeps track of the current context.
  *
@@ -53,7 +51,7 @@ var ReactContext = {
   withContext: function(newContext, scopedCallback) {
     var result;
     var previousContext = ReactContext.current;
-    ReactContext.current = merge(previousContext, newContext);
+    ReactContext.current = Object.assign({}, previousContext, newContext);
     try {
       result = scopedCallback();
     } finally {
diff --git a/src/core/ReactDefaultBatchingStrategy.js b/src/core/ReactDefaultBatchingStrategy.js
index f88e9e7732..790b57f883 100644
--- a/src/core/ReactDefaultBatchingStrategy.js
+++ b/src/core/ReactDefaultBatchingStrategy.js
@@ -22,7 +22,6 @@ var ReactUpdates = require('ReactUpdates');
 var Transaction = require('Transaction');
 
 var emptyFunction = require('emptyFunction');
-var mixInto = require('mixInto');
 
 var RESET_BATCHED_UPDATES = {
   initialize: emptyFunction,
@@ -42,12 +41,15 @@ function ReactDefaultBatchingStrategyTransaction() {
   this.reinitializeTransaction();
 }
 
-mixInto(ReactDefaultBatchingStrategyTransaction, Transaction.Mixin);
-mixInto(ReactDefaultBatchingStrategyTransaction, {
-  getTransactionWrappers: function() {
-    return TRANSACTION_WRAPPERS;
+Object.assign(
+  ReactDefaultBatchingStrategyTransaction.prototype,
+  Transaction.Mixin,
+  {
+    getTransactionWrappers: function() {
+      return TRANSACTION_WRAPPERS;
+    }
   }
-});
+);
 
 var transaction = new ReactDefaultBatchingStrategyTransaction();
 
diff --git a/src/core/ReactLegacyElement.js b/src/core/ReactLegacyElement.js
index 28ef28de28..84a6bf3504 100644
--- a/src/core/ReactLegacyElement.js
+++ b/src/core/ReactLegacyElement.js
@@ -99,7 +99,7 @@ function proxyStaticMethods(target, source) {
       if (typeof value === 'function') {
         var bound = value.bind(source);
         // Copy any properties defined on the function, such as `isRequired` on
-        // a PropTypes validator. (mergeInto refuses to work on functions.)
+        // a PropTypes validator.
         for (var k in value) {
           if (value.hasOwnProperty(k)) {
             bound[k] = value[k];
diff --git a/src/core/ReactNativeComponent.js b/src/core/ReactNativeComponent.js
index 0735e2050a..d6f79a4456 100644
--- a/src/core/ReactNativeComponent.js
+++ b/src/core/ReactNativeComponent.js
@@ -19,7 +19,6 @@
 "use strict";
 
 var invariant = require('invariant');
-var mergeInto = require('mergeInto');
 
 var genericComponentClass = null;
 // This registry keeps track of wrapper classes around native tags
@@ -34,7 +33,7 @@ var ReactNativeComponentInjection = {
   // This accepts a keyed object with classes as values. Each key represents a
   // tag. That particular tag will use this class instead of the generic one.
   injectComponentClasses: function(componentClasses) {
-    mergeInto(tagToComponentClass, componentClasses);
+    Object.assign(tagToComponentClass, componentClasses);
   }
 };
 
diff --git a/src/core/ReactPropTransferer.js b/src/core/ReactPropTransferer.js
index ddba15ef49..11e7a55809 100644
--- a/src/core/ReactPropTransferer.js
+++ b/src/core/ReactPropTransferer.js
@@ -21,7 +21,6 @@
 var emptyFunction = require('emptyFunction');
 var invariant = require('invariant');
 var joinClasses = require('joinClasses');
-var merge = require('merge');
 var warning = require('warning');
 
 var didWarn = false;
@@ -47,7 +46,7 @@ var transferStrategyMerge = createTransferStrategy(function(a, b) {
   // `merge` overrides the first object's (`props[key]` above) keys using the
   // second object's (`value`) keys. An object's style's existing `propA` would
   // get overridden. Flip the order here.
-  return merge(b, a);
+  return Object.assign({}, b, a);
 });
 
 /**
@@ -113,7 +112,7 @@ var ReactPropTransferer = {
    * @return {object} a new object containing both sets of props merged.
    */
   mergeProps: function(oldProps, newProps) {
-    return transferInto(merge(oldProps), newProps);
+    return transferInto(Object.assign({}, oldProps), newProps);
   },
 
   /**
diff --git a/src/core/ReactUpdates.js b/src/core/ReactUpdates.js
index ad4a3dfdd0..8b48d15e73 100644
--- a/src/core/ReactUpdates.js
+++ b/src/core/ReactUpdates.js
@@ -25,7 +25,6 @@ var ReactPerf = require('ReactPerf');
 var Transaction = require('Transaction');
 
 var invariant = require('invariant');
-var mixInto = require('mixInto');
 var warning = require('warning');
 
 var dirtyComponents = [];
@@ -80,8 +79,9 @@ function ReactUpdatesFlushTransaction() {
     ReactUpdates.ReactReconcileTransaction.getPooled();
 }
 
-mixInto(ReactUpdatesFlushTransaction, Transaction.Mixin);
-mixInto(ReactUpdatesFlushTransaction, {
+Object.assign(
+  ReactUpdatesFlushTransaction.prototype,
+  Transaction.Mixin, {
   getTransactionWrappers: function() {
     return TRANSACTION_WRAPPERS;
   },
diff --git a/src/event/__tests__/EventPluginRegistry-test.js b/src/event/__tests__/EventPluginRegistry-test.js
index 43ed309f2e..f98420ba45 100644
--- a/src/event/__tests__/EventPluginRegistry-test.js
+++ b/src/event/__tests__/EventPluginRegistry-test.js
@@ -18,8 +18,6 @@
 
 "use strict";
 
-var merge = require('merge');
-
 describe('EventPluginRegistry', function() {
   var EventPluginRegistry;
   var createPlugin;
@@ -29,7 +27,7 @@ describe('EventPluginRegistry', function() {
     EventPluginRegistry._resetEventPlugins();
 
     createPlugin = function(properties) {
-      return merge({extractEvents: function() {}}, properties);
+      return Object.assign({extractEvents: function() {}}, properties);
     };
   });
 
diff --git a/src/test/ReactDefaultPerfAnalysis.js b/src/test/ReactDefaultPerfAnalysis.js
index 5a23916cd3..b86a17dfbe 100644
--- a/src/test/ReactDefaultPerfAnalysis.js
+++ b/src/test/ReactDefaultPerfAnalysis.js
@@ -16,8 +16,6 @@
  * @providesModule ReactDefaultPerfAnalysis
  */
 
-var merge = require('merge');
-
 // Don't try to save users less than 1.2ms (a number I made up)
 var DONT_CARE_THRESHOLD = 1.2;
 var DOM_OPERATION_TYPES = {
@@ -71,7 +69,11 @@ function getExclusiveSummary(measurements) {
 
   for (var i = 0; i < measurements.length; i++) {
     var measurement = measurements[i];
-    var allIDs = merge(measurement.exclusive, measurement.inclusive);
+    var allIDs = Object.assign(
+      {},
+      measurement.exclusive,
+      measurement.inclusive
+    );
 
     for (var id in allIDs) {
       displayName = measurement.displayNames[id].current;
@@ -119,7 +121,11 @@ function getInclusiveSummary(measurements, onlyClean) {
 
   for (var i = 0; i < measurements.length; i++) {
     var measurement = measurements[i];
-    var allIDs = merge(measurement.exclusive, measurement.inclusive);
+    var allIDs = Object.assign(
+      {},
+      measurement.exclusive,
+      measurement.inclusive
+    );
     var cleanComponents;
 
     if (onlyClean) {
@@ -174,7 +180,7 @@ function getUnchangedComponents(measurement) {
   // the amount of time it took to render the entire subtree.
   var cleanComponents = {};
   var dirtyLeafIDs = Object.keys(measurement.writes);
-  var allIDs = merge(measurement.exclusive, measurement.inclusive);
+  var allIDs = Object.assign({}, measurement.exclusive, measurement.inclusive);
 
   for (var id in allIDs) {
     var isDirty = false;
diff --git a/src/test/ReactTestUtils.js b/src/test/ReactTestUtils.js
index 1c8516545c..756af946f1 100644
--- a/src/test/ReactTestUtils.js
+++ b/src/test/ReactTestUtils.js
@@ -29,8 +29,6 @@ var ReactTextComponent = require('ReactTextComponent');
 var ReactUpdates = require('ReactUpdates');
 var SyntheticEvent = require('SyntheticEvent');
 
-var mergeInto = require('mergeInto');
-
 var topLevelTypes = EventConstants.topLevelTypes;
 
 function Event(suffix) {}
@@ -327,7 +325,7 @@ function makeSimulator(eventType) {
       ReactMount.getID(node),
       fakeNativeEvent
     );
-    mergeInto(event, eventData);
+    Object.assign(event, eventData);
     EventPropagators.accumulateTwoPhaseDispatches(event);
 
     ReactUpdates.batchedUpdates(function() {
@@ -383,7 +381,7 @@ buildSimulators();
 function makeNativeSimulator(eventType) {
   return function(domComponentOrNode, nativeEventData) {
     var fakeNativeEvent = new Event(eventType);
-    mergeInto(fakeNativeEvent, nativeEventData);
+    Object.assign(fakeNativeEvent, nativeEventData);
     if (ReactTestUtils.isDOMComponent(domComponentOrNode)) {
       ReactTestUtils.simulateNativeEventOnDOMComponent(
         eventType,
diff --git a/src/test/reactComponentExpect.js b/src/test/reactComponentExpect.js
index c040e271eb..3613238b7c 100644
--- a/src/test/reactComponentExpect.js
+++ b/src/test/reactComponentExpect.js
@@ -21,8 +21,6 @@
 
 var ReactTestUtils = require('ReactTestUtils');
 
-var mergeInto = require('mergeInto');
-
 function reactComponentExpect(instance) {
   if (instance instanceof reactComponentExpect) {
     return instance;
@@ -38,7 +36,7 @@ function reactComponentExpect(instance) {
   expect(ReactTestUtils.isElement(instance)).toBe(false);
 }
 
-mergeInto(reactComponentExpect.prototype, {
+Object.assign(reactComponentExpect.prototype, {
   // Getters -------------------------------------------------------------------
 
   /**
diff --git a/src/utils/CallbackQueue.js b/src/utils/CallbackQueue.js
index 9d989b59ec..2558d02e1c 100644
--- a/src/utils/CallbackQueue.js
+++ b/src/utils/CallbackQueue.js
@@ -21,7 +21,6 @@
 var PooledClass = require('PooledClass');
 
 var invariant = require('invariant');
-var mixInto = require('mixInto');
 
 /**
  * A specialized pseudo-event module to help keep track of components waiting to
@@ -39,7 +38,7 @@ function CallbackQueue() {
   this._contexts = null;
 }
 
-mixInto(CallbackQueue, {
+Object.assign(CallbackQueue.prototype, {
 
   /**
    * Enqueues a callback to be invoked when `notifyAll` is invoked.
diff --git a/src/utils/LegacyImmutableObject.js b/src/utils/LegacyImmutableObject.js
index e7383ae911..a3ec75f24b 100644
--- a/src/utils/LegacyImmutableObject.js
+++ b/src/utils/LegacyImmutableObject.js
@@ -21,8 +21,6 @@
 
 var invariant = require('invariant');
 var isNode = require('isNode');
-var merge = require('merge');
-var mergeInto = require('mergeInto');
 var mergeHelpers = require('mergeHelpers');
 
 var checkMergeObjectArgs = mergeHelpers.checkMergeObjectArgs;
@@ -51,7 +49,7 @@ if (__DEV__) {
    * @constructor
    */
   LegacyImmutableObject = function LegacyImmutableObject(initialProperties) {
-    mergeInto(this, initialProperties);
+    Object.assign(this, initialProperties);
     deepFreeze(this);
   };
 
@@ -100,7 +98,7 @@ if (__DEV__) {
    */
   LegacyImmutableObject.set = function(immutableObject, put) {
     assertLegacyImmutableObject(immutableObject);
-    var totalNewFields = merge(immutableObject, put);
+    var totalNewFields = Object.assign({}, immutableObject, put);
     return new LegacyImmutableObject(totalNewFields);
   };
 
@@ -112,7 +110,7 @@ if (__DEV__) {
    * @constructor
    */
   LegacyImmutableObject = function LegacyImmutableObject(initialProperties) {
-    mergeInto(this, initialProperties);
+    Object.assign(this, initialProperties);
   };
 
   /**
@@ -126,7 +124,7 @@ if (__DEV__) {
   LegacyImmutableObject.set = function(immutableObject, put) {
     assertLegacyImmutableObject(immutableObject);
     var newMap = new LegacyImmutableObject(immutableObject);
-    mergeInto(newMap, put);
+    Object.assign(newMap, put);
     return newMap;
   };
 }
diff --git a/src/utils/OrderedMap.js b/src/utils/OrderedMap.js
index 22af8f2aaf..d0b769642d 100644
--- a/src/utils/OrderedMap.js
+++ b/src/utils/OrderedMap.js
@@ -19,7 +19,6 @@
 "use strict";
 
 var invariant = require('invariant');
-var mixInto = require('mixInto');
 
 var PREFIX = 'key:';
 
@@ -483,7 +482,7 @@ var OrderedMapMethods = {
   }
 };
 
-mixInto(OrderedMapImpl, OrderedMapMethods);
+Object.assign(OrderedMapImpl.prototype, OrderedMapMethods);
 
 var OrderedMap = {
   from: function(orderedMap) {
diff --git a/src/utils/__tests__/Transaction-test.js b/src/utils/__tests__/Transaction-test.js
index 39115cd242..df8263f4d4 100644
--- a/src/utils/__tests__/Transaction-test.js
+++ b/src/utils/__tests__/Transaction-test.js
@@ -19,14 +19,12 @@
 "use strict";
 
 var Transaction;
-var mixInto;
 
 var INIT_ERRORED = 'initErrored';     // Just a dummy value to check for.
 describe('Transaction', function() {
   beforeEach(function() {
     require('mock-modules').dumpCache();
     Transaction = require('Transaction');
-    mixInto = require('mixInto');
   });
 
   /**
@@ -53,7 +51,7 @@ describe('Transaction', function() {
       this.secondCloseParam = INIT_ERRORED;  // WILL be set to something else
       this.lastCloseParam = INIT_ERRORED;    // WON'T be set to something else
     };
-    mixInto(TestTransaction, Transaction.Mixin);
+    Object.assign(TestTransaction.prototype, Transaction.Mixin);
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
         {
@@ -102,7 +100,7 @@ describe('Transaction', function() {
       this.secondCloseParam = INIT_ERRORED;  // WILL be set to something else
       this.lastCloseParam = INIT_ERRORED;    // WILL be set to something else
     };
-    mixInto(TestTransaction, Transaction.Mixin);
+    Object.assign(TestTransaction.prototype, Transaction.Mixin);
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
         {
@@ -163,7 +161,7 @@ describe('Transaction', function() {
       this.secondCloseParam = INIT_ERRORED;  // WILL be set to something else
       this.lastCloseParam = INIT_ERRORED;    // WILL be set to something else
     };
-    mixInto(TestTransaction, Transaction.Mixin);
+    Object.assign(TestTransaction.prototype, Transaction.Mixin);
     // Now, none of the close/inits throw, but the operation we wrap will throw.
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
@@ -227,7 +225,7 @@ describe('Transaction', function() {
     var TestTransaction = function() {
       this.reinitializeTransaction();
     };
-    mixInto(TestTransaction, Transaction.Mixin);
+    Object.assign(TestTransaction.prototype, Transaction.Mixin);
     var exceptionMsg = 'This exception should throw.';
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
@@ -256,7 +254,7 @@ describe('Transaction', function() {
       this.reinitializeTransaction();
       this.firstCloseParam = INIT_ERRORED; // WILL be set to something else
     };
-    mixInto(TestTransaction, Transaction.Mixin);
+    Object.assign(TestTransaction.prototype, Transaction.Mixin);
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
         {
@@ -284,7 +282,7 @@ describe('Transaction', function() {
     var NestedTransaction = function() {
       this.reinitializeTransaction();
     };
-    mixInto(NestedTransaction, Transaction.Mixin);
+    Object.assign(NestedTransaction.prototype, Transaction.Mixin);
     NestedTransaction.prototype.getTransactionWrappers = function() {
       return [{
         initialize: function() {
diff --git a/src/utils/mixInto.js b/src/utils/mixInto.js
deleted file mode 100644
index b582d1ed1c..0000000000
--- a/src/utils/mixInto.js
+++ /dev/null
@@ -1,34 +0,0 @@
-/**
- * Copyright 2013-2014 Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- * @providesModule mixInto
- */
-
-"use strict";
-
-/**
- * Simply copies properties to the prototype.
- */
-var mixInto = function(constructor, methodBag) {
-  var methodName;
-  for (methodName in methodBag) {
-    if (!methodBag.hasOwnProperty(methodName)) {
-      continue;
-    }
-    constructor.prototype[methodName] = methodBag[methodName];
-  }
-};
-
-module.exports = mixInto;
diff --git a/src/vendor/core/emptyFunction.js b/src/vendor/core/emptyFunction.js
index c9d89f2215..c06b760dae 100644
--- a/src/vendor/core/emptyFunction.js
+++ b/src/vendor/core/emptyFunction.js
@@ -16,8 +16,6 @@
  * @providesModule emptyFunction
  */
 
-var copyProperties = require('copyProperties');
-
 function makeEmptyFunction(arg) {
   return function() {
     return arg;
@@ -31,7 +29,7 @@ function makeEmptyFunction(arg) {
  */
 function emptyFunction() {}
 
-copyProperties(emptyFunction, {
+Object.assign(emptyFunction, {
   thatReturns: makeEmptyFunction,
   thatReturnsFalse: makeEmptyFunction(false),
   thatReturnsTrue: makeEmptyFunction(true),
diff --git a/src/vendor/immutable/Immutable.js b/src/vendor/immutable/Immutable.js
index 7c7559a6b5..fcd1f287c9 100644
--- a/src/vendor/immutable/Immutable.js
+++ b/src/vendor/immutable/Immutable.js
@@ -19,7 +19,6 @@
 var invariant = require('invariant');
 var isNode = require('isNode');
 var keyOf = require('keyOf');
-var mergeInto = require('mergeInto');
 
 var SECRET_KEY = keyOf({_DONT_EVER_TYPE_THIS_SECRET_KEY: null});
 
@@ -67,7 +66,7 @@ class Immutable {
   static mergeAllPropertiesInto(destination, propertyObjects) {
     var argLength = propertyObjects.length;
     for (var i = 0; i < argLength; i++) {
-      mergeInto(destination, propertyObjects[i]);
+      Object.assign(destination, propertyObjects[i]);
     }
   }