TypeScript 4.9 - Checks For Equality on NaN | Release Report

Dimitri Mitropoulos explains how TypeScript 4.9 prevents errors by catching direct equality checks against NaN.

TypeScript is getting smarter all the time. In 4.9 it's got some new insights about how to handle equality checks for the NaN value. Since nothing is ever equal to NaN (including even NaN itself!), TypeScript can save you from yourself when you try to include NaN in equality or inequality checks. 00:00 a fun interview question 01:06 a quirk of all number systems 02:36 common solutions to this problem 03:20 NaN equality checks in JavaScript 04:04 IEEE-754 floating point number spec 04:42 TypeScript's insights for NaN equality checks 05:21 Number.isNaN saves the day 06:22 TypeScript is still just JavaScript 06:55 audience question: is TypeScript breaking the IEEE 754 spec? 07:42 audience comment: semantic meaning of NaN 08:16 audience comment: `typeof NaN` is still `number` 09:30 audience comment: JS Wat's `baNaNa` Dimitri Mitropoulos is a functional programming enthusiast that aims to not annoy his colleagues by forcing Ramda into every package. In his free time he likes to write Rust programs, eat soup dumplings, and can often be found in the woodshop making furniture for his friends and family. Recorded on November 1st at Cahoots (cahoots.com) in Ann Arbor, Michigan. Discord: discord.gg/tmhGfR4Dye Twitter: twitter.com/MiTypeScript Mastodon: fosstodon.org/@MichiganTypeScript Instagram: instagram.com/michigantypescript TikTok: tiktok.com/@michigantypescript