Also, HaXe is the only viable technology which enables a high-quality canvas-based applications which mirror native applications (while also permitting compilation to those native applications).
Even then, this still leaves C/emscripten which can also fulfill those requirements, and with similar output sizes (I've tested both and compared the sizes of the resulting web versions, seems that both have an overhead of 1-2 MB for a small graphical application). It depends on what you're planning to do, but one problem I found with Haxe is that it's lacking a good general-purpose UI library that also works well on the web target. Only lower-level graphics libraries.