Is there a way to create nominal types in TypeScript that extend primitive types?

Question

Say I have two types of numbers that I\'m tracking like latitude and longitude. I would like to represent these variables with the basic num

Answer 1

You can approximate opaque / nominal types in Typescript using a helper type. See this answer for more details:

// Helper for generating Opaque types.
type Opaque = T & { __opaque__: K };

// 2 opaque types created with the helper
type Int = Opaque;
type ID = Opaque;

// works
const x: Int = 1 as Int;
const y: ID = 5 as ID;
const z = x + y;

// doesn't work
const a: Int = 1;
const b: Int = x;

// also works so beware
const f: Int = 1.15 as Int;

Here's a more detailed answer: https://stackoverflow.com/a/50521248/20489

Also a good article on different ways to to do this: https://michalzalecki.com/nominal-typing-in-typescript/