filter-arr.js

// Description:
// Given an integer array arr and a filtering function fn, return a filtered array filteredArr.
// The fn function takes one or two arguments:
// arr[i] - number from the arr
// i - index of arr[i]
// filteredArr should only contain the elements from the arr for which the expression fn(arr[i], i) evaluates to a truthy value. A truthy value is a value where Boolean(value) returns true.
// Please solve it without the built-in Array.filter method.

// Example 1:
// Input: arr = [0,10,20,30], fn = function greaterThan10(n) { return n > 10; }
// Output: [20,30]
// Explanation:
// const newArray = filter(arr, fn); // [20, 30]
// The function filters out values that are not greater than 10

// Example 2:
// Input: arr = [1,2,3], fn = function firstIndex(n, i) { return i === 0; }
// Output: [1]
// Explanation:
// fn can also accept the index of each element
// In this case, the function removes elements not at index 0

// Example 3:
// Input: arr = [-2,-1,0,1,2], fn = function plusOne(n) { return n + 1 }
// Output: [-2,0,1,2]
// Explanation:
// Falsey values such as 0 should be filtered out

// my solution:
var filter = function (arr, fn) {
  const filteredArr = [];
  for (let i = 0; i < arr.length; i++) {
    if (fn(arr[i], i)) {
      filteredArr.push(arr[i]);
    }
  }
  return filteredArr;
};