Typescript: What is the correct type for a Timeout?

In a Web Browser app, setTimeout returns a number.

This setup requires the DOM library (or equivalent).

In a NodeJS app, setTimeout returns a NodeJS.Timeout.

npm install @types/node --save-dev`. 

For this case, I will give you 2 options:

1. Define type of debounceResize as return type of setTimeout, use ReturnType native generic.

let debounceResize: ReturnType<typeof setTimeout>;

2. Use window.setTimeout instead of only setTimeout. window.setTimeout returns a number.

let debounceResize: number;

debounceResize = window.setTimeout(() => {}, 1000);