The original source code for jQuery. Including annotations from Jon Resig:
I want to just take a moment to note how little has changed in how these functions work, at an API level. There’s a strong chance that you could take circa-2006 jQuery-using code and drop in a modern version and have it still work. Granted much more was added later on, as it increased in scope beyond my simple use cases, but almost all of the API that we see here was left intact. I’m definitely proud of the fact that the API was “good enough” to last over the next decade — and beyond.
It’s kind of amazing that the original version of jQuery wasn’t even 700 lines of code — a good reminder that even really big projects start out small. Via Jeremy Kieth.