My first serious web programming job was creating a complicated web-app with lots of JavaScript that had to support IE-4/4.5/5 and Netscape Communicator.
I don't miss those days at all... A major client of my employer around 2000-2001 was "standardized" on Netscape 4.06. And I was expected to make stack diagrams and Gantt charts. I wrote an abstraction library just to draw boxes on the screen targeting the IE/NN 4x/5x differences, having to cover the screen in NN while "drawing" just to prevent the flickering effect causing someone a seizure. ILayer/IFrames, ugh... dynamic forms were horrible, having to mirror multiple forms into a composite hidden field form next to the submit button.
So many hacks... Not to mention the IE 5.0.0 select api bug, or the later uncatchable error in IE8's JSON parser... those were some rough years.
Well, JavaScript didn't have a ton of features back then to muddy up the waters. So that helped. And no frameworks kept things simple.
The most complex part was a dynamic query builder where you could pick columns and various kinds of filters. We could have gone to the server each time the user changed the query, but I found it a lot snappier to do it all with document.write().
For a while, JavaScript was shunned by a lot of web shops. Applets and Flash were the future! Then Google Maps came out and showed what you could really do, and JS became cool again.
FWIW that app is still running to this day: https://resultview.q2labsolutions.com/resultview/logon/logon...
Vanilla JavaScript just works. Marvel at the circa 2001 Login button!