Algorithm
30 Days of JavaScript
Apply Transform over Each Element in Array

2635. Apply Transform Over Each Element in Array

Tags

  • Basic Array Transformations

Link

https://leetcode.com/problems/apply-transform-over-each-element-in-array/description/?envType=study-plan-v2&envId=30-days-of-javascript (opens in a new tab)

Question

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 an integer.

Answer

JavaScript

/**
 * @param {number[]} arr
 * @param {Function} fn
 * @return {number[]}
 */
var map = function (arr, fn) {
  let newArr = [];
  for (let i = 0; i < arr.length; i++) {
    newArr.push(fn(arr[i], i));
  }
  return newArr;
};
/**
 * @param {number[]} arr
 * @param {Function} fn
 * @return {number[]}
 */
var map = function (arr, fn) {
  for (let i = 0; i < arr.length; ++i) {
    arr[i] = fn(arr[i], i);
  }
  return arr;
};
Allow One Function CallArray Prototype Last