I ported a project to TypeScript last week, and was very impressed with the language. I had rejected it out of hand in favor of coffeescript, but didn't realize how modern and expressive a type system they had created. Bug-catching gains were immediate, and while it took a little bit to get comfortable with its ins and outs, I'm excited about coding everything in JS again.

100% agree. As much as I love CoffeeScript, the intellisense and type hinting is an invaluable aid to our team. TypeScript is the answer to team collaboration on large projects. There's no more guessing what the arguments are, whether an argument is an object or string. Source maps is icing on the cake.

Have you tried https://www.jetbrains.com/webstorm/ ? I find it quite good at intellisense.

I would be absolutely delighted if type hinting made its way into CoffeeScript somehow.

Yeah, my dream is a Typescript + Coffeescript dialect.

I am impressed at how expressive interfaces and structural sub-typing are for Javascript, even though there is still no way to express a heterogeneous array. However, I have been very disappointed at how weak their type inference is and that they have no plans to improve it. http://typescript.codeplex.com/workitem/329

Heterogenous arrays can have very poor performance on some JavaScript VMs, particularly Google's V8. If you can avoid them in performance sensitive code, it's a good idea to do so.

For more information, see this excellent talk: http://v8-io12.appspot.com/

You can't make the inference you suggest in the bug. It's not always valid. What if you set the variable in the function?

This line of type inference is very problematic in languages like JavaScript. Your statement that you expected "modern type inference" makes it sound like you only have practical knowledge (maybe you've used ML or Haskell?), not theoretical background. You should review the literature.

I just did a presentation on TypeScript last night and the biggest pushback was debugging in JavaScript. I told them source maps where coming, I had no idea it would be so soon though. Maybe next month we can have generics!

This is huge! If there's one thing I miss about developing on the .NET stack is the fantastic usage of breakpoints. It saves a lot of time.

Having to use "print_r", or "console.log" is a pain in the ass.

Chrome's web debugger has break points. You can also place the word " debugger " in your code and chrome will break at the debugger.

No GP but, personally I don't feel it's as good as the VS debugger. Unless I am missing something you still have to type into the console to get the value of things you want instead of just hovering over things, or bringing up quick watch in visual studio.

Also I'd imagine (haven't used it yet!) if you change the source in visual studio while debugging it would save to a file, while I cannot do that in chrome. I think I've heard it's possible in chrome, but never really seen how.

Chrome's debugger is darned near a full dev environment at this point, it's just not documented all that well and a lot of the best stuff has only been added recently. You can even edit the files, run the edited code, and save the changes locally.

You know what's really good about the Chrome debugger? It's free and it's on every computer that runs Chrome. Visual Studio is neither of those. I really wish they built VS functionality into the IE debugger.

As far as showing variables, one trick I use a lot is to set a conditional breakpoint where the code to execute is `console.log(stuff), false` so that it just logs stuff but doesn't ever stop. That's also handy for "fixing" variable values without stopping.

VS is free , well , at least the express version , which is more than enough for web development. personally , I prefer to debug JS in VS than than in Chrome. The chrome debugger never really worked well for me or did stuff as I would expect them.

Does it have conditional breakpoints and tracing breakpoints? I find the latter mostly entirely eliminate the need to sprinkle printf-equivalents to follow complex flows. For full disclosure I work on VS, but not the debugger or in Javascript, and I really don't know about Chrome's dev tools, but having seen some people's approaches to debugging JS, it feels like it is in a relatively primitive state from what I am used to in other languages.

Yes and yes.

I see conditional breakpoints, where are the tracing variety?

EDIT: Oh, I see, from your comment you are just leveraging the conditional breakpoint to ad-hoc them. That works but is a bit uglier than truly supported tracing breakpoints, and wouldn't appear to offer things like dumping the callstack to the output window or only triggering the print out only when specific conditions are met (i.e. a conditional tracing breakpoint). I suppose you could ad-hoc that as well by surrounding the print code with an if(<condition>) { print stuff }, <condition>. Works, hacky, but works I suppose.

VS is free.

You can hover in the Chrome Debugger (https://www.dropbox.com/s/fsr2cnf22exakts/hover.png). And it looks like saving to files is possible too (https://github.com/NV/chrome-devtools-autosave).

You can hover over variables to get their value. There is a quick watch area in which you can add variables.

You can't change the source directly, but you can change the properties of an object and change global variables with the console.

https://developers.google.com/chrome-developer-tools/docs/sc...

http://stackoverflow.com/a/4949829/352087

I'll definitely look into that. If I can just hover over variables that would save me tremendous time.

Is there any concise typescript reference around? The playground doesn't showcase that much features. The language specification while extensive is not that great as a cheatsheet.

I read the language spec and skipped everything but the code samples. It wasn't too bad, but yeah, not a cheatsheet.

Hmm, which other languages/compilers do support source maps right now? CoffeeScript, HaXe, now TypeScript, anything else?

Google's Closure Compiler

GWT and Dart do as well