title: Why was ECMAScript 4th edition completely scrapped?
body: <p>I've been looking for some information regarding the scrapped ECMAScript 4th Edition without much success, even on SO.  I know Mozilla's JavaScript 1.7 implemented many (all?) of the new features offered in 4th Edition and I thought I remembered a good John Resig post on it but I can't seem to find it on his blog now.</p>
  
  <p>In particularly, I want to know why it was completely scrapped in favour of ECMA-262 5th Edition and why it wasn't just improved upon.  Some of the features are pretty cool, like generators, iterators, let, new assignment operators and (my particular favourite) destructuring assignment.</p>
  
  <p>I know all of those particular features would just throw errors in browsers with out-of-date ECMAScript implementations, but why not include them anyway with the knowlege that one day those implementations would be few and far between?  Were there other reasons too?  Are we likely to see some of the scrapped features reappear in a future release, or are vendors so scared of breaking compatibility that we will probably never see such improvements to the standard?</p>
  
  <p>As an aside, it would be nice to know some opinions on the matter, are you annoyed to see some features cut from the 5th Edition or do you think it's better this way?  Is it worth playing around with implementations of ECMAScript 4?</p>