And it's great!
In terms of performance testing, jsPerf is truly a gift for the programmers. Not only you can set up your own tests (like the one I made some time ago, to see if accessing the document via a cached variable is faster than doing it directly), but you get access to tests made by others. It's a good idea to check that page from time to time to see what various improvements people tested and remember the best solution, so you can also use it in the future.
And last but certainly not least...
Thanks to that site I found out about the "use strict" statement and other various helpful things that are more important than you might consider. It's a very big deal to have clean, structured and organized code. Even if you'll be the only one to maintain it, it will make your job easier in the future.