2626-array-reduce-transformation.js

/**
 * 2626. Array Reduce Transformation
 * https://leetcode.com/problems/array-reduce-transformation/
 * Difficulty: Easy
 *
 * Given an integer array nums, a reducer function fn, and an initial value init, return the final
 * result obtained by executing the fn function on each element of the array, sequentially,
 * passing in the return value from the calculation on the preceding element.
 *
 * This result is achieved through the following operations: val = fn(init, nums[0]),
 * val = fn(val, nums[1]), val = fn(val, nums[2]), ... until every element in the array has been
 * processed. The ultimate value of val is then returned.
 *
 * If the length of the array is 0, the function should return init.
 *
 * Please solve it without using the built-in Array.reduce method.
 */

/**
 * @param {number[]} nums
 * @param {Function} fn
 * @param {number} init
 * @return {number}
 */
var reduce = function(nums, fn, init) {
  let result = init;

  for (let i = 0; i < nums.length; i++) {
    result = fn(result, nums[i]);
  }

  return result;
};