嗨，欢迎来到React！

我认为您在这里遇到的问题并不是与React特定的，而是与新的ES2015模块语法有关。在创建React类组件时，出于大多数意图和目的，您可以认为在React.createClass功能上等同于class MyComponent extends React.Component。一种只是使用新的ES2015类语法，而另一种则使用ES2015之前的语法。

为了学习模块，我建议阅读一些有关新模块语法的文章以使其熟悉。这是一个很好的开始：http : //www.2ality.com/2014/09/es6-modules-
final.html。

简而言之，这些只是语法上的差异，但我将尝试快速浏览一下：

/**
 * This is how you import stuff.  In this case you're actually 
 * importing two things:  React itself and just the "Component" 
 * part from React.  Importing the "Component" part by itself makes it
 * so that you can do something like:
 *
 * class MyComponent extends Component ...
 * 
 * instead of...
 * 
 * class MyComponent extends React.Component
 * 
 * Also note the comma below
 */
import React, {Component} from 'react';


/**
 * This is a "default" export.  That means when you import 
 * this module you can do so without needing a specific module
 * name or brackets, e.g.
 * 
 * import Header from './header';
 *
 * instead of...
 *
 * import { Header } from './header';
 */
export default class Header extends Component {

}

/**
 * This is a named export.  That means you must explicitly
 * import "Header" when importing this module, e.g.
 *
 * import { Header } from './header';
 *
 * instead of...
 * 
 * import Header from './header';
 */
export const Header = React.createClass({

})

/**
 * This is another "default" export, only just with a 
 * little more shorthand syntax.  It'd be functionally 
 * equivalent to doing:
 *
 * const MyClass = React.createClass({ ... });
 * export default MyClass;
 */
export default React.createClass({

})