React的getDefaultProps和getInitialState

getDefaultProps 不是获取默认props，而是设置默认props，主要用在ES5的React写法中
getInitialState 不是获取默认State，而是设置初始的state，主要是用在ES5的React写法中

下面是ES5和ES6的写法对比

//ES5写法
var Video = React.createClass({
    getDefaultProps: function(){
        return {
            autoPlay: false,
            maxLoops: 10
        }
    },
    getInitialState: function(){
        return {
            loopsRemaining: this.props.maxLoops
        }
    },
    propTypes: {
        autoPlay: React.PropTypes.bool.isRequired,
        maxLoops: React.PropTypes.number.isRequired,
        posterFrameSrc: React.PropTypes.string.isRequired,
        videoSrc: React.PropTypes.string.isRequired
    }
})

//ES6写法
class Video extends React.Component {
    static defaultProps = {
        autoPlay: false,
        maxLoops: 10
    }
    static propTypes = {
        autoPlay: React.PropTypes.bool.isRequired,
        maxLoops: React.PropTypes.number.isRequired,
        posterFrameSrc: React.PropTypes.string.isRequired,
        videoSrc: React.PropTypes.string.isRequired
    }
    //构造函数写法
    constructor(props){
        this.state = {
            ...
        }
    }
    //非构造函数写法
    state = {
        loopsRemaining: this.props.maxLoops
    }
}

//组件外部写法
Video.defaultProps = {
    autoPlay: false,
    maxLoops: 10
}