Everyone's capacity to pick up a new skill is going to be different. IMO 20 hours is not enough to be proficient in any language, let alone JS. I would completely ignore a resume that said anything like 20 hours of education.
Learning / getting good at a programming language is a life style. You don't need to live and breath it, but you need to work at learning it day in day out. This is why it tends to be easier to learn things on the job. You have a built in 40 hours / week commitment to learn it.
Further - learning a language doesn't mean you're good at it. Anyone can rattle off methods and functions built into a language. What makes a good programmer is the ability to take those things you learned and build stuff or talk intelligently about it. When the boss asks "how would you approach X problem" the difference between answers from someone with 20 hours and 10,000 hours of experience will be night and day.
Good programmers bring their years of experience with them to a problem / job and 20 or 100 hours just won't cut it. Being a problem solver is so much more important than memorizing the syntax for a language.