I haven't switched to coffeescript but I have worked on several coffeescript codebases. Its not the end of the world, but I don't prefer it. It is an unnecessary level of abstraction and is fragmenting js. It also seems the coffeescript users tend to use haml and sass as well. When I am working on those projects I feel like I am drowning in preprocessors and frequently encounter cryptic errors as a result.

I can't speak for haml, but sass is certainly a welcome tool in dealing with CSS, since it mostly uses CSS syntax, with sensible nesting to keep things orderly. sass takes what you already know and kicks it up one notch (perhaps two, if you want to use variables).

Overall, CoffeeScript has made JS development much more enjoyable for me. We had also integrated the compiler very nicely into our build script.

This resource has been invaluable: http://js2coffee.org/

I've used Coffeescript on a couple large Rails projects, and I'd rather stick with Javascript. I haven't encountered any terrible debugging hurdles, but it just seems like obfuscation. And unlike one of your other respondents, I love Sass and Haml. I have nothing against preprocessing per se, but I haven't yet figured out what value CS adds. I appreciate easier iteration, but that's about it. But considering how many people rave about it, I'm willing to learn....

I haven't used coffee script myself, but I think you'd be hard pressed to find someone that wrote something in CoffeeScript and regretted it. The biggest arguments against using CoffeeScript (or any language that compiles to JavaScript) that I seem to keep hearing are:

1. JavaScript isn't a very readable language. (I think this is untrue. I've seen some incredibly well written / structured JS) 2. Not everyone knows CoffeeScript, so when you put a project up on GitHub and it's written in CoffeeScript, it's difficult for people who only know the syntax of native JS to understand what's going on. (To counter this - a lot of projects that are written in CoffeeScript are bundled with the compiled JS code as well - which also happens to be very readable IMHO).

3. (biggest problem IMO): debugging in CS sucks right now. It would be a no-problem with SourceMap though, so we have to endure it just a few more months.

I hear this a lot, but seriously, have you ever had any real problems with debugging CS? The output is clear enough for anyone to know exactly where to go for the error.

It's a pain, still. I don't generate js files. When something like that happens, I have to go back to command-line, type 'coffee ...coffee', open generated js file and see where the problem was.

That's your problem right there ;) When you're using CoffeeScript, you're absolutely supposed to generate all of your JS files. -- For the same reason why you don't run all of your JavaScript via eval() while you're developing.

Try using `coffee --watch` instead.

OK then. I have already 7-8 tabs in my terminal open all the time (a few for servers, some for redis, some for mongod, some for vi, some for other tools, some for debugging, etc.), so I guess another tab wouldn't hurt (I'm not a fan of running processes in the background).

doubtful. As a JS dev, I often find myself in situations where I wish I was working with CS instead.

However, this article isnt advocating CoffeeScript (well it is, but it doesnt actually make a case for it), its advocating using a statically typed language. CS gives you classes, but thats not a big deal (module pattern makes it trivial to implement classes in JS).

To scale your web app, the author is advocating writing your apps in Java, C# and actionscript.

Now that I think of it, this is a really poorly laid out argument. It spends most of the time arguing for static typing, then throws in CoffeeScript as a sop to the people who will flame him for advocating Java/C#/AS.

This article doesn't really look like it's worth my time to read in depth so I won't comment on it directly. But as far as javascript goes Coffeescript makes a lot of the idiosyncracy of javascript that create constant cognitive friction go away. I personally can't find any good reasons to not use coffeescript.

I switched to CoffeeScript and continue to use it for 90% of my projects. CS shines in the application domain, but don't use it when writing modules or a complicated application where you'll be debugging lots of logic errors.

I don't know what this article is about (looks like it's not worth reading), but I've switched to CS (IcedCoffeeScript, to be precise) for my Node.js app (a behemoth of an app!), and am much much happier. Sure, it has problems too, but they are more tolerable than having to do (if typeof(x)=='function' && x!=null) over and over again IMO, and the vast majority of them will be gone when we have SourceMaps (which shouldn't take long, maybe a couple more months).

I switched to Coffeescript and rarely if ever look back...

It's hard to imagine having much regret about a switch to CS since it would be so easy to convert your code back to JS if you ever needed to (and since you could do so incrementally).

CoffeeScript is a syntax, not a language.

His arguments have to do with the semantics of JavaScript, which are identical to the semantics of CoffeeScript.

Coffeescript has a very similar object model, but it does alter (fix) the semantics of variable binding and expression statements and some unusably broken operators, and those involve treating Javascript more like a compilation target than an equivalent dialect.

Yesss running s/==/===/g...very semantically different ;)

Personally I think its great because it is just a different syntax for the same semantics.