Cool way to check for leap years in JavaScript

Published on in JavaScript

Spoiler: new Date(year, 1, 29).getDate() === 29.

I stumbled upon a tweet by Colin DeCarlo about a cool way to check if a given year is a leap year (code by JleCoRyl3):

function isLearYear(year) {
  return new Date(year, 1, 29).getDate() === 29

Quite clever! Though a bit confusing at first because months are 0-indexed. Maybe a code comment would be in order.

The tweet is what inspired me to start doing TypeScript exercises on Exercism.