How to loop a list in react

React loop list method: 1. map loop, the code is [let MyDom =arr.map((item,index)=>]; 2. for loop, the code is [for(var i= 0;i

• ##This method is suitable for all brands of computers

React loop list method:

1.map loop

<script type="text/babel">
        let arr=["吃饭","睡觉","喝水"]
        let MyDom =arr.map((item,index)=>{
            return <p>{item}</p>
        })
        ReactDOM.render(MyDom,document.getElementById("demoReact"))
    </script>

Traversal can be displayed on the page, console But an error was reported. The reason is that you have to set a unique key to facilitate subsequent operations on the array.

After adding the key value, no error will be reported.

 <script type="text/babel">
        let arr=["吃饭","睡觉","喝水"]
        let MyDom =arr.map((item,index)=>{
        //key值必须是独一无二的
            return <p key={index}>{item}</p>
        })
        ReactDOM.render(MyDom,document.getElementById("demoReact"))
    </script>

If you want to change the code after return to Is it easy to just press Enter on the next line?

//直接回车换行
return 
<p key={index}>{item}</p>

Of course it’s not easy to use. The solution is to use () to wrap the element, and it can be displayed normally after changing the line.

So develop a habit: no matter how you change Add () without line breaks

//用括号包裹住换行元素
 let MyDom =arr.map((item,index)=>{
            return (
                <p key={index}>{item}</p>)
        })

2.for in loop

 function fun(){
            let newarr=[];
            for(let index in arr){
               newarr.push(<p key={index}>{arr[index]}</p>)
            }
            return newarr;
        }
        
        ReactDOM.render(fun(),document.getElementById("demoReact"))

3.for loop

 function fun(){
            let newarr=[];
            for(var i=0;i<arr.length;i++){
               newarr.push(<p key={i}>{arr[i]}</p>)
            }
            return newarr;
        }

4.for each loop

 function fun(){
            arr.forEach(a=>{
             console.log(a);
            })
        }

Related free learning recommendations:

javascript(video)

The above is the detailed content of How to loop a list in react. For more information, please follow other related articles on the PHP Chinese website!