I program in Java and it doesn't make sense to me to think about learning a Java library or a framework without knowing the actual language the thing is built with. Same goes for C. I always avoided JavaScript simply because I wasn't interested in the client side of things but that has changed now.
I'm confused as to how and why do people avoid learning JavaScript and instead jump right ahead with a library like JQuery ?
How can I program without knowing the features of JS, what is a prototype based language, functions as first class citizens, OOP, closures, etc.
Also, are most of the things today in the client-side world built with the help of third party libraries?
Best Answer
jQuery's primary role is to normalize the DOM API which is the one thing browsers haven't agreed on for over a decade (until IE9 came out). It's better thought of as a tool than a library. It's basically just a factory function that returns an adapter merged with a bit of decorator that wraps and normalizes the DOM object API with lots of cruft reduction and some additional goodies like the animate function and an event system that lets you fire and listen for new events on the fly on any object without even defining them somewhere first.
What it doesn't do is help you with writing more complex, maintainable app-oriented code (well, the event thing is neat-o but easy enough to DIY), use objects well, or use any of the core ECMA spec obects that really form the basis for the core language of JavaScript.
Among proper JavaScript devs, it takes very little time to filter out the devs who are going to be useful on a project from web designers or CMS-only devs gunning for a salary increase by doing awful things with a tool they'd rather not understand under the hood if they can avoid it.
Also, the DOM API is pretty verbose with method names that practically write their own documentation (by approaching paragraph length basically), which is a good thing, IMO. We want the core native stuff to be obvious and spelled out. But the tedious nature of writing with it encourages us to use JavaScript to do something it's very good at. Eliminate cruft, normalize, and bend the API to a paradigm that works better for us. I personally think jQuery did a bang-up job of this compared to most of its contemporaries and that you can learn a lot about JavaScript (like how to keep your objects really lightweight as far as memory is concerned) by studying jQuery under the hood.
But I wouldn't use it as a pre-fab UI library namespace. And I wouldn't discard loops in favor of using .each on everything. And I often downshift to DOM API methods when JQuery is adding work without really eliminating cruft which brings up one of the most important features of jQuery to those of us who actually know what we're doing. It doesn't get in your way when you don't want it there.
But make no mistake. If you don't know how to do it without jQuery you're at best an entry-level JavaScript/client-side dev. On the flip-side if you only know JavaScript and only have minimal understanding of CSS, you better be focused on something other than UI problems.
Edit: I realize I focused on JQ a bit too much for a question that was asked more generally.
Most other popular JS tools/libraries/frameworks are either UI libraries, none of which I'm a big fan of (too inflexible typically), and rapid-application building frameworks that apply concepts from MVC or similar patterns. I'd rather DIY architecture personally (and I'm a little wary of this model-binding in templates trend) but these new frameworks aren't the sorts of things implemented by JS devs who can't handle code problems that require JS-literacy themselves I would wager.