[nxn]

To preface, let's say that "application-scale" means something like the following: your server outputs a single html file that only contains references to js files and css (i.e., the minimum to get the app to work right), from then on all data operations are ajax calls to a server side API, while the entire state of the app, all UI/markup components included, is maintained via JS.

I've worked on a couple of these applications, they almost always end up having some fake-class system that provides mechanisms for encapsulation, code sharing, and namespacing. There's often almost a hundred of these fake classes defined with thousands of instances living in memory. I grant you that you can use things like the module pattern to accomplish those requirements -- in fact, if you couldn't, then I wouldn't be here talking about it because I'd be writing Java applets instead. But the lack of having static typing to catch simple errors and enabling basic refactoring tools (like renaming something without having to use a regular expression which took 2 hours to "perfect", or simply switching argument orders, etc) was the absolute worst. I've spent countless hours debugging problems that occurred because something like a string was accidentally passed when an array was expected, and only having the actual runtime error occur 50 function calls later because something like "cat"[0] was working fine up to that point. Static typing would have caught that before I even ran the app.

Anyway, these types of apps perhaps aren't as common as websites, but they exist and therefore there is a need for statically typed languages for the browser.