Mount and unmount - reactjs

App.js

/**
 * Created by clarico on 30/04/2015.
 */
var Button = React.createClass({
    getInitialState: function () {
        return {val : 0}
    },
    update : function () {
        this.setState({val: this.state.val +1});
    },
    componentWillMount: function () {
        console.log('mounting')
    },
    render:function(){
        console.log("rendering...");
        return <button onClick={this.update}>{this.state.val}</button>
    },
    componentDidMount : function () {
        console.log('mounted');
    },
    componentWillUnmount : function () {
        console.log('bye!')
    }
 });

var App = React.createClass({
    mount : function () {
        React.render(<Button />, document.getElementById("app"));
    },
    unmount : function () {
        React.unmountComponentAtNode(document.getElementById("app"));
    },

    render:function(){
        return (
            <div>
                <button onClick={this.mount}>Mount</button>
                <button onClick={this.unmount}>UnMount</button>
                <div id="app"></div>
            </div>
        )
    } 
 });

React.render(<App/>,document.body );