I got my start in 2008 with Prototype and the effects library Scriptaculous (built on Prototype). Prototype would actually alter built-in JavaScript objects, which could cause problems if you introduced scripts not built with Prototype. It was still a breathe of fresh air compared to using vanilla JS back then, with all of the incompatibilities between browsers. Once jQuery was introduced, and decided to wrap objects rather than alter them, it really changed the way development was done. I still build all my web apps using progressive enhancement, and try to use static HTML as much as possible so apps still work without JS. It really doesn't take any extra time to build this way, and I separate my backend logic so I could easily move to a SPA if a client desired it (NOTE: most clients really don't care as long as it works, and they don't have to wait too long for page loads).
