Dropbox is a high-profile convert to CoffeeScript, a language that has the elegance of Ruby or Python but compiles into clean JavaScript in order to run in the browser. The Dropbox team says that CoffeeScript fixes many of JavaScript’s “syntactic problems.” In addition, a porting exercise reduced 23,437 lines of JavaScript to 18,417 lines of CoffeeScript, code, and this brevity was considered the “strongest argument” in favour – even though many of those eliminated lines were just curly braces and parentheses.

In order to port the code, the team used the Js2coffee tool; a bit of a brain-twist, a tool to convert JavaScript to a language that later compiles back to JavaScript.

The whole post is worth a read, and gives before and after examples.

Consider also the following:

Google’s Dart is an alternative web language that compiles to JavaScript, as is Google Web Toolkit

Microsoft’s Office Web Apps are written in C# compiled to JavaScript with a version of Script#. Microsoft’s Roslyn compiler as a service project lets you copy and paste VB code as C# and vice versa, and is already also being used to compile C# as JavaScript. Microsoft’s Anders Hejlsberg is rumoured to be working on a JavaScript project.

JavaScript seems to be becoming the new Common Language Runtime, not that Microsoft’s .NET CLR is going away, but rather that JavaScript now better fulfils the goal: pick whatever language you like and run it in the browser. 

PostScript:

I was intrigued to note that the Dropbox post does not render properly in Internet Explorer 10. For some reason that must appeal to geeky humour, it includes code spoken as audio, but the audio tags fail:

instead of

Possible reasons: the Dropbox page has a DOCTYPE of XHTML 1.0, and the files are in .wav format where IE is documented only to support MP3 or MP4. IE10 therefore refuses to play the audio, which works fine in Google Chrome and Mozilla Firefox.

The significance of this is not so much the technicalities, but rather what it implies about how many people now use IE in the community most likely to read this post.