Before jQuery there was Prototype.js, part of early AJAX support in RoR, which fixed inconsistencies in how browsers could fetch data, especially in the era between IE 5 and 7 (native JS `XMLHttpRequest` was only available from IE 7 onwards, before that it was some ActiveX thing. The other browsers supported it from the get go). My memory is vague, but it also added stuff like selectors, and on top of that was script.aculo.us which added animations and other such fanciness.
jQuery took over very quickly though for all of those.