题解 | #添加元素#

function insert(arr, item, index) {

let newArr = []

for(var i=0; i<arr.length; i++) {

newArr.push(arr[i])

}

if(index >= newArr.length) {

newArr.push(item)

} else {

for(var j=newArr.length; j>=index;j--) {

newArr[j+1] = newArr[j]

}

newArr[index] = item

}

return newArr

}