View http://wibblycode.wordpress.com/2013/01/01/the-state-of-javascript-package-management/
One notable thing about JavaScript in the browser compared to other popular languages is the almost lack of a standard library. Even some of the most common tasks can require a fair chunk of code. You can write it all yourself, but crafting cross-browser compatible code remains a minefield. If you don’t want to do it yourself, what can you do?
I’d wager that package management had a decent role in legitimizing JavaScript for many developers. I think that applies to PHP as well, but that’s another topic. If you’re anything like me you’re not able to keep up with the bleeding edge hardcore JavaScript development projects out there, and the established ones are just barely on the fringe of your radar. It’s not that I’m not using them, I’m just not sure of the fundamental differences between them. This article answered a lot of questions.