I wouldn't really consider anything involving the DOM to be a JS fundamental. That's a browser fundamental, and even then, it's like, what do you want? I can use `document.write('hello world')` and replace the entire body. Or append it as a text node with `document.body.append`. Or create an element and add it. This is a pretty silly question and something people should just spend 2 seconds looking up on the rare occasion they need to do it.

I currently work with devs who've done things like create a Map and then assign properties directly instead of using .set and .get.. I'd say that shows a pretty significant lack of fundamentals