Yeah, the difference is jQuery is not a language, it does not do everything. Dart can also be stand alone and even make console applications (I assume the same with Coffeescript but I havent used it), its an entirely new language that just happens to compile to javascript. I wasn't really suggesting it as an alternate to javascript, everyone should learn js if they are doing something based on a website simply because Dart is inefficient if it is a small script. But yeah when you get to making anything OOP in javascript I find it just turns into a total clusterf*ck since it isnt really designed the same way as Java or C# (But in my opinion they are the best implementation of OOP).
Where the heck have you been?