A speed optimization is not a "quirk". Compare asm.js for more insight.

An exile from tribe martalec ? joined ncontex i see ? :)

asm.js consists of a strict subset of the JavaScript language ... Almost all of the current applications based on asm.js are C/C++ applications compiled to asm.js using Emscripten or Mandreel. With that in mind, the kind of applications that are going to target asm.js in the near future are those that will benefit from the portability of running in a browser but which have a level of complexity for which a direct port to JavaScript would be infeasible...

The OPs construct ain't got nothing with asm.js, and asm.js aint got nothing to do with 99.999% javascript programmers