The problem I have with "output to Javascript" languages is that debugging becomes hell. Line numbers no longer correspond to each other, for example.

A slightly less-hellish but still annoying problem is that I often poke at things directly from the console when bugs happen, and this helps me a lot in debugging. However poking at the console requires using JavaScript, which is fine, but it would drive me nuts to have to code in one language (e.g. CoffeeScript, TypeScript, Python) and debug in another (JavaScript) and switch my brain back and forth every few minutes. So I've ended up largely sticking with writing code directly in JavaScript.

Any good solutions to this? Are there replacements to the Chrome JavaScript console that supports those other languages?

Purescript is interesting, I've been trying to build a project in it over the last few months. Since it's still pre 1.0, it has proven difficult but understandably so. It's mostly due to arcane/vague error messages (which they're in the process of dealing with), painfully long compile times, (imo) a few missing features, and incomplete young libraries.

On the flip side, with the state of libraries and all, it's provided me with a real incentive to get involved in open source, by having to contribute patches to said libraries and getting actively involved in general discussion.

Edit:

Just so I don't come off as mostly negative, I do enjoy having purescript as another statically typed option on the client side with close semantics to javascript. It's also been nice having a some kind of parsec like library on the client side (purescript-parsing), which was the main reason I chose purescript for this project in the first place.

plus its semantics lie pretty close to javascript. Most importantly because it's strict instead of lazy. Eventhough its strict it has a very haskelly feel. Both in syntax and type system. Also I think strict semantics is the way to go for efficient Functional Reactive Programming.

Furthermore, Purescript's FFI is really nice to use and it's really easy to bind to existing javascript libraries.

PureScript is community is nice and active. They are also discussing a lot with the `virtual-dom` guys to bring react/om/mercury-like functionality to purescript [0] and it's quite freakin awesome.

Seriously I'd take purescript for javascript any day. I think it's great that we FP folks can finally do frontend dev :-)

[0] - https://github.com/slamdata/purescript-halogen

Also, ClojureScript.