old_contents: import React from "react";
  import ReactDOM from "react-dom";
  
  class Hello extends React.Component {
    render(){
      return (
        <div>
          Hello World! Hello {this.props.year}! Hello {this.props.name}!
        </div>
      );
    }
  }
  
  ReactDOM.render(
    <Hello name="Ivan" year={2016} />,
    document.getElementById('app')
  );
  
new_contents: import React from "react";
  import ReactDOM from "react-dom";
  
  /**
   * [USER_DATA Github 用户数据]
   * @type {Array} ｛name, username, image}
   */
  let USER_DATA = [
    {
      name: 'Tyler McGinnis',
      username: 'tylermcginnis',
      image: 'https://avatars0.githubusercontent.com/u/2933430?v=3&s=460'
    },
    {
      name: 'Ruan YiFeng',
      username:'ruanyf',
      image: 'https://avatars3.githubusercontent.com/u/905434?v=3&s=460',
    },
    {
      name: 'Ivan',
      username: 'Ivanwangcy',
      image: 'https://avatars3.githubusercontent.com/u/6278969?v=3&s=460'
    }
  ];
  
  /**
   * 简介 头像
   */
  class ProfilePic extends React.Component {
    render(){
      return <img src={this.props.imageUrl} style={{height: 100, width: 100}}/>
    }
  }
  
  /**
   * 简介 链接
   */
  class ProfileLink extends React.Component {
    render(){
      return (
        <div>
          <a href={'https://www.github.com/' + this.props.username}>
            {this.props.username}
          </a>
        </div>
      );
     }
  }
  
  /**
   * 简介 姓名
   */
  class ProfileName extends React.Component {
    render(){
      return <div>{this.props.name}</div>;
    }
  }
  
  /**
   * github 个人简介
   */
  class Avatars extends React.Component {
    render() {
      console.log(this.props);
      var avatarList = this.props.users.map((value) => {
        return (
          <li key={value.username}>
            <ProfilePic imageUrl={value.image}></ProfilePic>
            <ProfileName name={value.name}></ProfileName>
            <ProfileLink username={value.username}></ProfileLink>
          </li>
        );
      });
      return (
        <ul>
          {avatarList}
        </ul>
      );
    }
  }
  
  ReactDOM.render(
    <Avatars users={USER_DATA} />,
    document.getElementById('app')
  );
  
subject: add github userinfo