import React,{ Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import * as serviceWorker from './serviceWorker';

class Focus extends Component{
  constructor(props){
    super(props);
    this.focusFn=this.focusFn.bind(this);
  }

  focusFn(){
    .refs.myInput.focus();
  }

  render(){
    return(
      <div>
        <input type="text" ref="myInput" />
        <br/>
        <button onClick={this.focusFn}>点我</button>
      </div>
    )
  }
}

  ReactDOM.render(
    <div>
       <Focus />
    </div>,document.getElementById('example')
  );

serviceWorker.unregister();