JS doesn't type check, generate an AST, or even minifies anything until the user runs the code. If you just write JS in notepad then immediately send it over to your users, then yeah, there's no build in JS.

But if your idea of writing software involves:

* type checking, linting and otherwise ensuring properties of the code before even running it.

* testing code before deploying it.

* turning it from text into a representation that's more compact and safer to run.

* generating documentation.

Then you'll definitely need a build, and a very complex one for that matter, in JS world. Have you ever seen a JS project without any sort of build in a professional context?

And you'll need a big IDE to help you make sense of anything because JS doesn't even have a "compiler" or "helper tool" that'll give you any help to navigate and understand the code base.