React的getDefaultProps和getInitialState

getDefaultProps 不是獲取預設props，而是設定預設props，主要用在ES5的React寫法中
getInitialState 不是獲取預設State，而是設定初始的state，主要是用在ES5的React寫法中

下面是ES5和ES6的寫法對比

//ES5寫法
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寫法
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
    }
    //建構函式寫法
    constructor(props){
        this.state = {
            ...
        }
    }
    //非建構函式寫法
    state = {
        loopsRemaining: this.props.maxLoops
    }
}

//元件外部寫法
Video.defaultProps = {
    autoPlay: false,
    maxLoops: 10
}