React 组件(Components) 和 属性(Props)

function formatDate(date) {
  return date.toLocaleDateString();
}
function Avatar(props) {
  return (
    <img className="Avatar" src={props.user.avatarUrl} alt= {props.user.name} />
  );
}
function UserInfo(props){
  return (
   <div className="UserInfo">
        <Avatar user={props.user} />
        <div className="UserInfo-name"> {props.user.name} </div>
   </div>
  );
}
function Comment(props) {
  return (
    <div className="Comment">
      <UserInfo user={props.author} />
      <div className="Comment-text"> {props.text} </div>
      <div className="Comment-date"> {formatDate(props.date)} </div>
    </div>
  );
}

const comment = {
  date: new Date(),
  text: 'I hope you enjoy learning React!',
  author: {
    name: 'Hello Kitty',
    avatarUrl: 'http://placekitten.com/g/64/64'
  }
};
ReactDOM.render(
  <Comment date={comment.date} text={comment.text} author={comment.author} />,
  document.getElementById('root')
);

prop
prop 是组件的对外接口(property)
state
state 是组件的内部状态

对外用prop ，内部用 state