2634. Filter Elements from Array

This problem involves implementing a function similar to Array.prototype.filter but without using the built-in method. The goal is to return a new array that only includes elements that return a truthy value when passed into the filtering function.

📄 Problem Statement

Given an integer array arr and a function fn, return a new array filteredArr such that:

filteredArr only contains the elements from arr for which fn(arr[i], i) returns a truthy value.

Do not use Array.prototype.filter().

💡 Example


Input:
arr = [0, 10, 20, 30]
fn = function greaterThan10(n) { return n > 10 }

Output:
[20, 30]

🧠 Explanation

We loop through the input array and pass each element and its index into the function fn. If the return value is truthy, we include that element in a new array. The final result is returned after the loop finishes.

✅ My Solution


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