[tav]

Whilst the concept of setImmediate is nice, the current implementation in IE isn't properly integrated with the rest of the event loop — resulting in broken behaviour when you use it in combination with setTimeout [1], DOM events, etc.

In contrast, using MutationObserver results in correct behaviour on all modern browsers and relatively minimal delays — between 0.002ms and 0.007ms according to an OS X only micro-benchmark I did last month [2].

And, yes, it would be great if we could call a builtin instead of hacking on top of MutationObserver, but it isn't that ugly:

  if MutationObserver
    $div = root.document.createElement 'div'
    observer = new MutationObserver tick
    observer.observe $div, attributes: true
    scheduleTick = ->
      $div.setAttribute 'class', 'tick'
      return
  else
    scheduleTick = ->
      setTimeout tick, 0
      return

In conclusion, I agree that a feature like setImmediate would be great. But given IE's broken implementation and a viable workaround in modern browsers, I see no need to rush it. I'd rather they focused on: new features like Object.observe; improving the performance of old features like Object.seal; and finalising some of the ES7 ideas like exposing the event loop!

[1] http://codeforhire.com/2013/09/21/setimmediate-and-messagech...

[2] https://gist.github.com/tav/9719011