数组函数map封装实现

function map(arr,callback){
    console.log(arr)
    let re = []
    for(let i = 0;i<arr.length;i++){
       re.push(callback(arr[i],i))
    }
    return re
}

<script>
    let arr = [1,2,3,4,5]
    const result = map(arr,(item,index) =>{
        return item * 10
    })
    console.log(result) // [10, 20, 30, 40, 50]
</script>