How do you explicitly set a new property on `window` in TypeScript?

Question

I setup global namespaces for my objects by explicitly setting a property on window.

window.MyNamespace = window.MyNamespace || {};

Answer 1

For those using the Angular CLI it's straightforward:

src/polyfills.ts

declare global {
  interface Window {
    myCustomFn: () => void;
  }
}

my-custom-utils.ts

window.myCustomFn = function () {
  ...
};

If you're using IntelliJ, you also needed to change the following setting in the IDE before your new polyfills pick up:

> File 
> Settings 
> Languages & Frameworks 
> TypeScript 
> check 'Use TypeScript Service'.