yield keyword/command in JavaScript 1.7

Anyone has a functional sample of using "yield" command in JavaScript
1.7 ? Ideally some sample of context preservation on setTimeout - if I
am not completely off the loop with the functionality of this new
command. The googled sources like
http://developer.mozilla.org/en/docs/New_in_JavaScript_1.7
http://www.zorched.net/2006/08/04/javascript-17-in-firefox-20/
http://aptana.com/reference/api/JSKeywords.yield%20statement.html
left my mind as innocent as it was before on the subject , sorry.
Maybe I just didn't read them right.
.