this, self, window, global, globalThis, etc.

TL;DR: In JavaScript (browser runtimes, at least), this, self, window, frame, and globalThis all point to the same value (the Window object).

Why do they all exist then? Per MDN:

Historically, accessing the global object has required different syntax in different JavaScript environments. On the web you can use window, self, or frames - but in Web Workers only self will work. In Node.js none of these work, and you must instead use global...

The globalThis property provides a standard way of accessing the global this value (and hence the global object itself) across environments.

I’ve been thinking more about JavaScript runtimes lately. I’d like to confidently know when I can use what (language features and APIs). My takeway here is when in doubt, use globalThis.