iterating NodeList's
When JavaScript got array iterators like Array.prototype.forEach I was extremely happy. But not for long. What made me just happy was the inability to do even document.links.forEach(). Don't even mention the likes of getElementsByName. That's when I started using the inelegant things like toArray. Though I liked better to add forEach in NodeList.prototype or to monkey-patch querySelectorAll. But now EcmaScript 2015 (aka EcmaScript 6) comes to the resque!
The new version should support following approach: for (var link of document.links) {}. You can even get something like your favourite closure-effect of a callback using for (let link of document.links) {}. And finally there's an elegant way to convert any array-like object to a proper array: [...document.links].filter().
I don't know about you, but I really look forward to the new features. By the way, I think the best articles on EcmaScript 6 are in the blog of Dr. Alex Rauschmayer.