React中受控组件

import React, { Component } from 'react'

export default class Input extends Component {
    constructor(props){
        super(props);
        this.state={
            username:""
        }
    }
    render() {
        return (
            <div>
                <form onSubmit={e=>this.handleSubmit(e)}>
                    <label htmlFor="usrname">
                        用户:<input 
                                type="text" 
                                id="username" 
                                onChange={e=>this.handleChang(e)}
                                value={this.state.value}/>
                    </label>
                    <input type="submit" value="提交" name="" id="" />
                </form>
            </div>
        )
    }
    handleSubmit(event){
        event.preventDefault()
    }
    handleChang(event){
        console.log(event.target.value);
        this.setState({
            username:event.target.value
        })
    }
}