2724. Sort By

Add a method sortBy(fn) to arrays in JavaScript. The method should return a new array sorted in ascending order based on the result of applying the function fn to each element.

📄 Problem Statement

Given an array arr and a function fn, return a new array sortedArr. The array should be sorted in ascending order based on the value returned by fn for each element.

Assume fn only returns numbers.
Assume no two elements will return the same number when fn is applied.
Do not modify the original array.

💡 Example


[5, 4, 1, 2, 3].sortBy(x => x)
// ➞ [1, 2, 3, 4, 5]

[{"x": 1}, {"x": 0}, {"x": 5}].sortBy(obj => obj.x)
// ➞ [{"x": 0}, {"x": 1}, {"x": 5}]

🧠 Explanation

The function creates a shallow copy of the original array using slice() or spread syntax, then sorts that copy using JavaScript’s built-in sort method with a custom comparator based on fn.

✅ Your Solution


/**
 * @param {Function} fn
 * @return {Array}
 */
Array.prototype.sortBy = function(fn) {
    return [...this].sort((a, b) => fn(a) - fn(b));
};