[Array] Apply Transform Over Each Element in Array (map 구현하기)

https://leetcode.com/problems/apply-transform-over-each-element-in-array/

Apply Transform Over Each Element in Array - LeetCode

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] <= 109
• fn returns a number

 

solution

/**
 * @param {number[]} arr
 * @param {Function} fn
 * @return {number[]}
 */
var map = function(arr, fn) {
    const valArr = [];
    for(let i = 0; i < arr.length; i++) {
        const value = fn(arr[i], i);
        valArr.push(value);
    }
    return valArr;
};