There's really three distinctions, in my mind:

1) Libraries (jQuery/Prototype/MooTools/etc) (Beginning - ~2010ish)

2) Widget-frameworks (YUI, Dojo, jQueryUI, etc) (mid-2000s - ~2013ish)

3) Data-orientied Frameworks (Backbone-onwards) (~early 2010s - current)

Edit: (Four, maybe, if you divide 1 into a 1/0 era, with 0 being the "rando DHTML scripts that many didn't really understand" era)

Prototype, Dojo and mooTools!

Memories. I remember discovering any of these existed after doing an entire AJAX frontend site with raw JS that continued to work cross browser for the next 10 years. Made me full appreciate the value of those frameworks. IIRC JSON wasn't even really a thing yet.

I don't even think mooTools and friends were really frameworks as we know them today. They were really just some kind of standard library that let you plug in fancy UX widgets and stuff... I dunno if the distinction really matters though. But I do know they weren't even in the same league of frameworks like angular or react.

I guess the difference is these new frameworks are all about letting javascript generate virtually the entire page. MooTools and friends were designed where the majority of the page was old-fashioned HTML being spat out by the backend.

Yep, mochikit was another one that I liked.

I worked at a company around 2001 that was doing a full "Ajax" style frontend for a dashboard product for some industrial control systems. But it worked in IE only, as the Ajax pieces were not available on the other browsers yet.

To my mind MooTools and jQuery were roughly equivalent in functionality. Am I misremembering?

mootools was awesome. I always wondered why it was so fun(for me at least) to use.