Not enough. Its more fun to create software, but documentation is the part that no one likes. It is absolutely necessary, in particular when other work with your code.

And we have many stages of documentation: the project documentation (what is it, what does it, how, ...), the code doc, the rest-api doc. And it get really complex on further development. I think that is one reason for the small JS project explosion on npm / github of the last years.