content: /**
  "this.props" can ref the React Component Attr Object
  "getInitialState" is default React method,which contains the state of React Component
  "{}" is used to write React Program
  **/
  
  /**
  how to bind event on DOM in React:
  
  <input onChange={this.onChange} value={this.state.text}>
  **/
  
  import React from 'react';
  
  React.createClass({
  	render: () => {
  		return (
  			<ul>
  				{
  					this.props.items.map(item => {
  						return <li key={item.id}>{item.text}</li>;
  					})
  				}
  			</ul>
  		);
  	}
  });
  
  React.createClass({
  	getInitialState: () => {
  		return { items: [], text: '' };
  	},
  	onChange: e => {
  		this.setState({
  			text: e.target.value
  		});
  	},
  	handleSubmit: e => {
  		e.preventDefault();
  		var nextItems = this.state.items.concat([{ text: this.state.text, id: Date().now() }]);
  		var nextText = '';
  		this.setState({
  			items: nextItems, text: nextText
  		});
  	},
  	render: () => {
  		return '3';
  	}
  });
  