In any case, are you sure that JS generators should be considered a "future" thing? I just did a bit of research, and it sounds like you are talking about this proposal:
According to the following page, much/all of that proposal was included in JS 1.7, which was implemented in Firefox 2.0.
And FF 2.0 was released in October 2006. A quick check shows that my FF installation (3.6.22) supports generator functions, and the "yield" keyword, just fine, as long as I say