react 受控组件，双向绑定

学习视频：https://www.bilibili.com/video/BV1wy4y1D7JT?p=34

一、受控组件

onChange方法实现

    <script type="text/babel">
        //创建组件
        class Login extends React.Component{

            //初始化状态
            state = {
                username:'', //用户名
                password:'' //密码
            }

            //保存用户名到状态中
            saveUsername = (event)=>{
                this.setState({username:event.target.value})
            }

            //保存密码到状态中
            savePassword = (event)=>{
                this.setState({password:event.target.value})
            }

            //表单提交的回调
            handleSubmit = (event)=>{
                event.preventDefault() //阻止表单提交
                const {username,password} = this.state
                alert(`你输入的用户名是：${username},你输入的密码是：${password}`)
            }

            render(){
                return(
                    <form onSubmit={this.handleSubmit}>
                        用户名：<input onChange={this.saveUsername} type="text" name="username"/>
                        密码：<input onChange={this.savePassword} type="password" name="password"/>
                        <button>登录</button>
                    </form>
                )
            }
        }
        //渲染组件
        ReactDOM.render(<Login/>,document.getElementById('test'))
    </script>

每一个input都要写一个方法保存状态，对此处进一步优化:https://www.cnblogs.com/shining-feifan/p/16247122.html

二、非受控组件

    <script type="text/babel">
        //创建组件
        class Login extends React.Component{
            handleSubmit = (event)=>{
                event.preventDefault() //阻止表单提交
                const {username,password} = this
                alert(`你输入的用户名是：${username.value},你输入的密码是：${password.value}`)
            }
            render(){
                return(
                    <form onSubmit={this.handleSubmit}>
                        用户名：<input ref={c => this.username = c} type="text" name="username"/>
                        密码：<input ref={c => this.password = c} type="password" name="password"/>
                        <button>登录</button>
                    </form>
                )
            }
        }
        //渲染组件
        ReactDOM.render(<Login/>,document.getElementById('test'))
    </script>