Ask any web developer what their preferred JavaScript library is, the unanimous answer is jQuery. It does not matter how small or large the web site is, what the feature set is, developers tend to prefer jQuery as the base JavaScript framework as it reduces the complexity of code they need to write, it is well tested, has a ton of plug-ins, has a large development community and hence reduces the development time.
CoffeeScript is a programming language that transcompiles to JavaScript. The language adds syntactic sugar inspired by Ruby, Python and Haskell to enhance JavaScript's brevity and readability, as well as adding more sophisticated features like array comprehension and pattern matching. CoffeeScript compiles predictably to JavaScript and programs can be written with less code (typically 1/3 fewer lines) with no effect on runtime performance. Let me introduce some cool useful tutorials.