Ten years ago (or less) if you had proposed building ANYTHING beyond basic form field validatation logic in JavaScript you would have been laughed out of the room. JS/Node is popular now but it's a fad. Things that seem exciting are really just reinvented wheels when you look closely. That said it's not a bad idea to learn it. Just don't think it will be something you're using heavily in 5-10 years. Same is true of any other language in the space though.