array.js

'use strict';

const nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

/**
 *  loops through array using for loop and console logs each value in array
 * @param {*} arr
 */
function forLoop(arr) {
  for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
  }
}

/**
 *  loops through array using while loop and console logs each value in array
 * @param {*} arr
 */
function whileLoop(arr) {
  let iterator = 0;
  while (iterator < arr.length) {
    console.log(arr[iterator]);
    iterator++;
  }
}

/**
 * Takes in arr and callback, returns new array with each element of passed in array modified by callback
 * @param {*} arr
 * @param {*} callback
 * @return {*} newArr
 */
function map(arr, callback) {
  const newArr = [];
  for (const i in arr) {
    newArr[i] = callback(arr[i]);
  }
  return newArr;
}

/**
 *  takes in array and callback function that returns true/false
 *  returns new array with only values from original array that result in true via callback
 * @param {*} arr
 * @param {*} callback
 * @return {*} newArr
 */
function filter(arr, callback) {
  const newArr = [];
  for (const thing of arr) {
    if (callback(thing)) newArr.push(thing);
  }
  return newArr;
}

/**
 *  Calls the passed in callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
 * @param {*} arr
 * @param {*} callback
 * @param {*} initialCondition
 * @return {*} accumulator
 */
function reduce(arr, callback, initialCondition) {
  const givenInitial = (initialCondition === 0 || initialCondition);
  let accumulator = (givenInitial ? initialCondition : arr[0]);
  let i = (givenInitial ? 0 : 1);

  for (i; i < arr.length; i++) {
    accumulator = callback(accumulator, arr[i]);
  }
  return accumulator;
}


forLoop(nums);
whileLoop(nums);

// implicit return by the callback
const mapped = map(nums, (a) => a * 2);
console.log(mapped);

const filtered = filter(nums, (b) => !(b % 2));
console.log(filtered);

const reduced = reduce(nums, (acc, curr) => acc * curr, 0);
console.log(reduced);