Eh, I actually like JS but I have definitely forgotten to add a "var" or "let" a few times, or sometimes I will do it correctly, get a bit overzealous with cutting, and accidentally remove the initial var declaration.

I'm not saying that it breaks the language, but it definitely is irritating, especially if you're not using a linter.

That's all fine, but those are all workarounds for a design mistake in the language.