Filter Elements from Array - 2634

🔗LC2634 🟢 Easy 🧩 Pattern – Array Transformations

📅 Day 6/30 Days of JavaScript

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

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

Solution

TLDR – write a polyfill for Array.filter.

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

Filter Elements from Array – 2634

Example

Solution