The problems should be blatantly obvious to developers who have used languages other than JavaScript and PHP (which both have many of the same flaws).

Once you've studied and used languages like C, C++, Python, Java, C#, Haskell, Scheme, Erlang and Standard ML, you'll see what we mean when we say that JavaScript is a very flawed language. Pick any of its features, and compare that feature to the equivalent feature in the other languages. JavaScript's approach will generally be the worst of all of them.

Variable scoping, unavoidable global namespace pollution, === vs == insanity, etc.

Last week I learned about another crazy "feature": Function hoisting

http://elegantcode.com/2011/03/24/basic-javascript-part-12-f...

But how do libraries help you from that?

Kitchen sink libraries like jquery + jquery ui save you from having to write much JavaScript at all beyond basic glue code. The less JavaScript I write, the happier I am. This is in stark contrast to other languages I work in where I actually like to roll my own frameworks.