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 /* 
                高階函數(shù): 如果一個(gè)函數(shù)符合下面2個(gè)規(guī)范中的任何一個(gè)，那該函數(shù)就是高階函數(shù)
                1. 若A函數(shù), 接收的參數(shù)是一個(gè)函數(shù)， 那么A就可以稱之為高階函數(shù)
                2. 若A函數(shù)， 調(diào)用的返回值依然是一個(gè)函數(shù)，那么A就可以稱之為高階函數(shù)
                常見的高階函數(shù)： Promise,setTimeout. arr.map() .....
                函數(shù)的柯里化： 通過函數(shù)調(diào)用繼續(xù)返回函數(shù)的方式，實(shí)現(xiàn)多次接收參數(shù)最后統(tǒng)一處理的函數(shù)編碼形式
            */
            //受控組件: 隨著值的改變，自動(dòng)存儲(chǔ)到state中，需要用時(shí)，直接到this.state中取
            class Login extends React.Component{
                //初始化狀態(tài)
                state = {
                    username:'',
                    userpwd :''
                }
                //保存用戶名到狀態(tài)中
                //saveFormData的返回值依然是一個(gè)回調(diào)函數(shù):  高階函數(shù)  同時(shí)也是  函數(shù)的柯里化
                saveFormData = (dataType)=>{
                    console.log(dataType);
                    return (event)=>{ //event是React維護(hù)時(shí)幫我們生成一個(gè)參數(shù)對(duì)象
                        console.log(dataType,event.target.value);
                        this.setState({[dataType]:event.target.value})
                        //注意：在對(duì)象中讀取變量，必須用[]
                        //如： let a = "name"    const obj = {}  obj[a] = "小明"
                    }
                }
                handleSubmit = (event)=>{
                    event.preventDefault(); //阻止表單的提交事件  阻止默認(rèn)事件
                    const {username,userpwd} = this.state
                    console.log(`你的用戶名是：${username}, 密碼是: ${userpwd}`);
                }
                render(){
                    return (
                        <form action="http://www.guvo98.cn" onSubmit={this.handleSubmit}>
                           用戶名： <input onChange={this.saveFormData('username')} type="text" />
                           密碼：  <input  onChange={this.saveFormData('userpwd')} type="password" />
                           {/* onChange=  ： 這里無論怎么寫，要保證返回值必須是一個(gè)回調(diào)函數(shù) */}
                           <button>登陸</button>
                        </form>
                    )
                }
            }
            ReactDOM.render(<Login/>,document.getElementById("test"));

非高階函數(shù)的使用

class Login extends React.Component{
                //初始化狀態(tài)
                state = {
                    username:'',
                    userpwd :''
                }
               
                saveFormData = (dataType,event)=>{
                        this.setState({[dataType]:event.target.value})
                }
                handleSubmit = (event)=>{
                    event.preventDefault(); //阻止表單的提交事件  阻止默認(rèn)事件
                    const {username,userpwd} = this.state
                    console.log(`你的用戶名是：${username}, 密碼是: ${userpwd}`);
                }
                render(){
                    return (
                        <form action="http://www.guvo98.cn" onSubmit={this.handleSubmit}>
                           用戶名： <input onChange={event=>this.saveFormData('username',event)} type="text" />
                           密碼：  <input  onChange={event=>this.saveFormData('userpwd',event)} type="password" />
                           {/* onChange=  ： 這里無論怎么寫，要保證返回值必須是一個(gè)回調(diào)函數(shù) */}
                           <button>登陸</button>
                        </form>
                    )
                }
            }
            ReactDOM.render(<Login/>,document.getElementById("test"));