Maybe it is all in my head but I find that every time I come across a interesting code sample or solution to a problem, it is only usable if you I am willing to commit to a JS library such as JQuery or ProtoypeJS - or re-write it mysel in plain JS.
It seems it is not enough to know learn javascript, but then you have factor in the many variations in syntax that result from using the current flavor-of-the-week library.
This list is far from complete and seems to be a small subset when you think about Backbone, underscore, coffescript, xui and more: http://en.wikipedia.org/wiki/Comparison_of_JavaScript_frameworks
I'm not complaining (yet) but it seems that every week there is a new choice, especially now that you have mobile specific ones. I'm concerned that this might be a problem very soon... or do HN readers feel it will eventually consolidate a bit over time?