How to sort an array?

Q: How to sort an array?

// alphabetical sort const fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.sort(); // numerical sort const points = [40, 100, 1, 5, 25, 10]; points.sort(function(a, b){return a - b}); //random order const points = [40, 100, 1, 5, 25, 10]; points.sort(function(){return 0.5 - Math.random()});

Difficulty: 5/10

Array.prototype.sort, In-place Mutation, Comparator Functions

Example code:

Scenario Questions

0-2 years experience

1We have a list of user ages like `[9, 21, 100, 5]`. A junior developer wrote `ages.sort()` to display them in ascending order, but the UI is showing `[100, 21, 5, 9]`. What is happening under the hood here, and how would you fix it?
2Imagine you are building a React component that displays a list of products. You receive the products array from props, sort it by price using `products.sort(...)`, and render it. However, you notice that this is causing unexpected side effects elsewhere in the app where the same product list is used. Why is this happening, and how would you safely sort the array?

2-5 years experience

Follow-up Questions

What is the time and space complexity of the sorting algorithm used in modern JS engines like V8?
How does the default sort behavior handle 'undefined' or missing values in an array?
If you need to sort an array without mutating the original, what modern ES2023 array method would you use instead?