Union types let us tell TypeScript a value can be of one type, or another type.

Example:

const run = (a: number | string) => {
  //...
}

In this case the parameter a can be either a string, or a number, but nothing else.

Lessons in this unit:

0:	Introduction
1:	Your first TypeScript program
2:	Types
3:	Typing functions
4:	The editor helps you with type errors
5:	Running TypeScript code
6:	Valid types
7:	Type aliases and interfaces
8:	▶︎ Union types
9:	Typing arrays with generics
10:	The DX of editing TypeScript
11:	There's more...