react.js 给标识ref，获取内容

import React,{Component} from ‘react‘import ReactDOM from ‘react-dom‘class App extends Component{ ???//给一个初始化状态 ???constructor(){ ???????super(); ???????this.state={ ???????????result:0 ???????} ???} ???handChange=()=>{ ???????//获取input a的类容，这个a就是我们给的标识ref="a" ???????let a=this.refs.a.value||0; ???????let b=this.refs.b.value||0; ???????//改变状态，更新视图 ???????this.setState({result:parseFloat(a)+parseFloat(b)}) ???} ???render(){ ???????return ( ???????????<div> ???????????????<input type="text" ref="a" onChange={this.handChange}/> ???????????????+ ???????????????<input type="text" ref="b" onChange={this.handChange}/> ???????????????<p>{this.state.result}</p> ???????????</div> ???????) ???}}ReactDOM.render(<App/>,document.querySelector("#root"))