Turns out you can define types conditionally based on the type check against a different type. Let’s try it out on a fetch function that optionally takes a callback and can return either a void or a promise based on that callback.

• 00:00 Introduction
• 00:18 What are conditional types?
• 02:15 Importing libraries
• 03:15 fetchPokemon with conditionals
• 08:23 fetchPokemon with overloading
• 11:14 Outroduction

Conditional Types page: https://www.typescriptlang.org/docs/handbook/2/conditional-types.html
Code: https://github.com/jherr/no-bs-ts/tree/master/episode-18

#typescript