React:Each child in an array or iterator should have a unique "key" prop.

>  let arr = ["张飞", "关羽", "刘备"]
>         console.log(this);
> 
>   let result = arr.map(function (val, ind) {
>         return <li>{val}</li>
>     })
>     console.log(result);。

然后

 {result}

使用他