Extending TypeScript Global object in node.js

Question

As of node@16 the NodeJS.Global interface has been removed in favor of globalThis.

You can declare new global variable in a module file as:

declare global {
  var NEW_GLOBAL: string;
}

And in a non-module file (no top-level import/export) as:

declare var NEW_GLOBAL: string;

Important note: variable must be declared as var. let and const variables don’t show up on globalThis.