createClass: function (spec) {var Constructor = function (props, context, updater) {// 触发自动绑定if (this.__reactAutoBindPairs.length) {bindAutoBindMethods(this);}// 初始化参数this.props = props;this.context = context;this.refs = emptyObject;  // 本组件对象的引用，可以利用它来调用组件的方法this.updater = updater || ReactNoopUpdateQueue;// 调用getInitialState()来初始化state变量this.state = null;var initialState = this.getInitialState ? this.getInitialState() : null;this.state = initialState;};// 继承父类Constructor.prototype = new ReactClassComponent();Constructor.prototype.constructor = Constructor;Constructor.prototype.__reactAutoBindPairs = [];injectedMixins.forEach(mixSpecIntoComponent.bind(null, Constructor));mixSpecIntoComponent(Constructor, spec);// 调用getDefaultProps，并挂载到组件类上。defaultProps是类变量，使用ES6写法时更清晰if (Constructor.getDefaultProps) {Constructor.defaultProps = Constructor.getDefaultProps();}// React中暴露给应用调用的方法，如render componentWillMount。// 如果应用未设置，则将他们设为nullfor (var methodName in ReactClassInterface) {if (!Constructor.prototype[methodName]) {Constructor.prototype[methodName] = null;}}return Constructor;},

<div className="title" ref="example"><span>123</span>    // 原生DOM组件，首字母小写<ErrorPage title='123456' desc={[]}/>    // 自定义组件，首字母大写
</div>

React.createElement('div',    // type,标签名,原生DOM对象为String{className: 'title',ref: 'example'},   // config，属性React.createElement('span', null, '123'),   // children，子元素React.createElement(// type,标签名,React自定义组件的type不为String.// _errorPage2.default为从其他文件中引入的React组件_errorPage2.default,    {title: '123456',desc: []})   // children，子元素
)

ReactElement.createElement = function (type, config, children) {var propName;// 初始化参数var props = {};var key = null;var ref = null;var self = null;var source = null;// 从config中提取出内容，如ref key propsif (config != null) {ref = config.ref === undefined ? null : config.ref;key = config.key === undefined ? null : '' + config.key;self = config.__self === undefined ? null : config.__self;source = config.__source === undefined ? null : config.__source;// 提取出config中的prop，放入props变量中for (propName in config) {if (config.hasOwnProperty(propName) && !RESERVED_PROPS.hasOwnProperty(propName)) {props[propName] = config[propName];}}}// 处理children，挂到props的children属性下// 入参的前两个为type和config，后面的就都是children参数了。故需要减2var childrenLength = arguments.length - 2;if (childrenLength === 1) {// 只有一个参数时，直接挂到children属性下，不是array的方式props.children = children;} else if (childrenLength > 1) {// 不止一个时，放到array中，然后将array挂到children属性下var childArray = Array(childrenLength);for (var i = 0; i < childrenLength; i++) {childArray[i] = arguments[i + 2];}props.children = childArray;}// 取出组件类中的静态变量defaultProps，并给未在JSX中设置值的属性设置默认值if (type && type.defaultProps) {var defaultProps = type.defaultProps;for (propName in defaultProps) {if (props[propName] === undefined) {props[propName] = defaultProps[propName];}}}// 返回一个ReactElement对象return ReactElement(type, key, ref, self, source, ReactCurrentOwner.current, props);
};

var ReactElement = function (type, key, ref, self, source, owner, props) {var element = {// This tag allow us to uniquely identify this as a React Element$$typeof: REACT_ELEMENT_TYPE,// ReactElement对象上的四个变量，特别关键type: type,key: key,ref: ref,props: props,// Record the component responsible for creating this element._owner: owner};return element;
}

// 初始化组件对象，node是一个ReactElement对象，是节点元素在React中的表示
function instantiateReactComponent(node) {var instance;var isEmpty = node === null || node === false;if (isEmpty) {// 空对象instance = ReactEmptyComponent.create(instantiateReactComponent);} else if (typeof node === 'object') {// 组件对象，包括DOM原生的和React自定义组件var element = node;// 根据ReactElement中的type字段区分if (typeof element.type === 'string') {// type为string则表示DOM原生对象，比如div span等。可以参看上面babel转译的那段代码instance = ReactNativeComponent.createInternalComponent(element);} else if (isInternalComponentType(element.type)) {// 保留给以后版本使用，此处暂时不会涉及到instance = new element.type(element);} else {// React自定义组件instance = new ReactCompositeComponentWrapper(element);}} else if (typeof node === 'string' || typeof node === 'number') {// 元素是一个string时，对应的比如<span>123</span> 中的123// 本质上它不是一个ReactElement，但为了统一，也按照同样流程处理，称为ReactDOMTextComponentinstance = ReactNativeComponent.createInstanceForText(node);} else {// 无处理}// 初始化参数，这两个参数是DOM diff时用到的instance._mountIndex = 0;instance._mountImage = null;return instance;
}

var emptyComponentFactory;var ReactEmptyComponentInjection = {injectEmptyComponentFactory: function (factory) {emptyComponentFactory = factory;}
};var ReactEmptyComponent = {create: function (instantiate) {return emptyComponentFactory(instantiate);}
};ReactEmptyComponent.injection = ReactEmptyComponentInjection;ReactInjection.EmptyComponent.injectEmptyComponentFactory(function (instantiate) {// 前面比较绕，关键就是这句话，创建ReactDOMEmptyComponent对象return new ReactDOMEmptyComponent(instantiate);
});// 各种null，就不分析了
var ReactDOMEmptyComponent = function (instantiate) {this._currentElement = null;this._nativeNode = null;this._nativeParent = null;this._nativeContainerInfo = null;this._domID = null;
};

ReactDOMComponent.Mixin = {mountComponent: function (transaction, nativeParent, nativeContainerInfo, context) {},_createOpenTagMarkupAndPutListeners: function (transaction, props){},_createContentMarkup: function (transaction, props, context) {},_createInitialChildren: function (transaction, props, context, lazyTree) {}receiveComponent: function (nextElement, transaction, context) {},updateComponent: function (transaction, prevElement, nextElement, context) {},_updateDOMProperties: function (lastProps, nextProps, transaction) {},_updateDOMChildren: function (lastProps, nextProps, transaction, context) {},getNativeNode: function () {},unmountComponent: function (safely) {},getPublicInstance: function () {}
}

var ReactCompositeComponentMixin = {// new对应的方法，创建ReactCompositeComponent对象construct: function(element) {},mountComponent,   // 初始挂载组件时被调用，仅一次performInitialMountWithErrorHandling, // 和performInitialMount相近，只是多了错误处理performInitialMount,  // 执行mountComponent的渲染阶段，会调用到instantiateReactComponent，从而进入初始化React组件的入口getNativeNode,unmountComponent, // 卸载组件，内存释放等工作receiveComponent,performUpdateIfNecessary,updateComponent,  // setState后被调用，重新渲染组件attachRef,    // 将ref指向组件对象，这样我们就可以利用它调用对象内的方法了detachRef,    // 将组件的引用从全局对象refs中删掉，这样我们就不能利用ref找到组件对象了instantiateReactComponent，  // 初始化React组件的入口，在mountComponent时的渲染阶段会被调用
}

var ReactDOMTextComponent = function (text) {this._currentElement = text;this._stringText = '' + text;
};_assign(ReactDOMTextComponent.prototype, {mountComponent,receiveComponent,getNativeNode,unmountComponent
}