生命周期构造函数:
	1. componentWillMount	组件挂载前
	2. componentDidMount	组件挂载后
	3. componentWillUpdate	组件更新前
	4. componentDidUpdate	组件更新后
	5. componentWillUnmount	组件卸载

<script type="text/babel">
    function destory(){
        ReactDOM.render(
            <span>销毁留下的垃圾...</span>,
            document.querySelector('#root')
        )
    }

    class MyComponent extends React.Component{
        constructor(props){
            super(props);
            this.state={
                count:10
            };
        }

        componentWillMount(){
            console.log('组件挂载前');
        }

        componentDidMount(){
            console.log('组件挂载后')
        }

        componentWillUpdate(){
            console.log('组件更新前');
        }

        componentDidUpdate(){
            console.log('组件更新后');
        }

        componentWillUnmount(){
            console.log('组件卸载');
        }

        fnClick(){
            this.setState({
                count:this.state.count+1
            })
        }
        render(){
            return (<div>
                <h3>{this.state.count}</h3>
                <button onClick={this.fnClick.bind(this)}>更新</button>
                <button onClick={destory}>销毁</button>
            </div>)
        }
    }

    ReactDOM.render(
        <MyComponent />,
        document.querySelector('#root')
    )
</script>

<script type="text/babel">
    function destory(){
        ReactDOM.render(
            <span>销毁留下的垃圾...</span>,
            document.querySelector('#root')
        )
    }

    class MyComponent extends React.Component{
        constructor(props){
            super(props);
            this.state={
                count:10
            };
        }

        componentWillMount(){
            console.log('组件挂载前');
        }

        componentDidMount(){
            console.log('组件挂载后')
        }

        componentWillUpdate(){
            console.log('组件更新前');
        }

        componentDidUpdate(){
            console.log('组件更新后');
        }

        componentWillUnmount(){
            console.log('组件卸载');
        }

        fnClick(ev){
            this.setState({
                count:this.state.count+1
            })
            ev.nativeEvent.stopImmediatePropagation();
        }
        render(){
            return (<div>
                <h3>{this.state.count}</h3>
                <button onClick={this.fnClick.bind(this)}>更新</button>
            </div>)
        }
    }

    ReactDOM.render(
        <MyComponent />,
        document.querySelector('#root')
    )

    document.onclick=function(){
        destory();
    };
</script>