2635. Apply Transform Over Each Element in Array 
¶
Problem
Given an integer array arr and a mapping function fn, return a new array with a transformation applied to each element.
The returned array should be created such that returnedArray[i] = fn(arr[i], i).
Please solve it without the built-in Array.map method.
Example 1:
Input: arr = [1,2,3], fn = function plusone(n) { return n + 1; }
Output: [2,3,4]
Explanation:
const newArray = map(arr, plusone); // [2,3,4]
The function increases each value in the array by one.
Example 2:
Input: arr = [1,2,3], fn = function plusI(n, i) { return n + i; }
Output: [1,3,5]
Explanation: The function increases each value by the index it resides in.
Example 3:
Input: arr = [10,20,30], fn = function constant() { return 42; }
Output: [42,42,42]
Explanation: The function always returns 42.
Constraints:
0 <= arr.length <= 1000-109 <= arr[i] <= 109fnreturns a number