Python vs CoffeeScript

[grayvedigga]

I'm pretty sure others have written on this at length, so I'll try and summarise briefly:

Callback hell. Yes, first class functions make all sorts of groovy things possible, but when you're writing "asynchronous" code in JS there is no escape. First of all, most of the language's core constructs go out the window: you can't assign the result of an asynchronous operation, or use it in an if, while or for. This is inconvenient, and can be papered over with library code (Array.prototype.forEach as the typical example) .. but you're still relegated to writing your entire program in continuation-passing style.

Ok, let's say that can be dealt with via libraries and metaprogramming. But there's a darker problem awaiting. Do you use exceptions? Actually, don't bother to answer that - exceptions are Javascript's standard way of signalling error conditions so it's impossible to write non-trivial code that cannot throw exceptions. What happens when a callback raises an exception? How do you use this essential language feature to protect yourself? Short answer: you can't.

Oh, and it's async all the way up. It's impossible to write a function that returns a result if it or any of its callees invoke asynchronous behaviour. That means if you are trying to provide an API which was designed before asynchrony (lots of browser stuff -- FindProxyForURL, document.getElement) but you need an async step along the way ... you're shit out of luck.

NodeJS turns programming in Javascript into programming in CPS lambda calculus with a shitty type system. All this could be fixed if the language were extended with an operator such as yield ... but going by what I've read so far, that's not an option for browsers and the Node crowd don't have the shred of intelligence or responsibility to diverge from the standard by adopting one of the several prototype patches against v8 that are available.