I'm talking about the beginning JS programmer. So it's quite likely that they don't understand the technology they're currently working on and thus have bigger

I'm talking about the beginning JS programmer. So it's quite likely that they don't understand the technology they're currently working on and thus have bigger problems evaluting the new one, as there's no good point of comparison. Also, I hope that the first project a JS newbie does isn't a 100'000 line app, but something more bite-sized, and thus you really don't have to wait months to get to use the new stack or tool. Quite often this kind of decision making happens when the project is 80% done and you have to face a few things that aren't that easy or your code has become a bit too complicated. And yes, the new tool could solve that and you might even end up re-implementing bits and pieces of that. This might not be the most effective use of your time, but it's a good learning experience.