Add static property to builtin type declaration

Question

TypeScript's built-in typings are currently missing AbortSignal.timeout. How does one write a .d.ts file to add it?

This doesn't work:

declare namespace AbortSignal {
  function timeout(milliseconds: number): AbortSignal;
}

Duplicate identifier 'AbortSignal'.(2300)
lib.dom.d.ts(1984, 11): 'AbortSignal' was also declared here.
lib.dom.d.ts(1996, 13): and here.

Answer 1

If you are using TypeScript 4.5+, you can solve this by installing @types/web as a lib replacement:

pnpm add @typescript/lib-dom@npm:@types/web --save-dev

npm install @typescript/lib-dom@npm:@types/web --save-dev

yarn add @typescript/lib-dom@npm:@types/web --dev

This requires you to have "dom" in the lib-section of your tsconfig.json.