Here’s one of the more famous libraries, it’s pretty much in use everywhere on the internet right now.
When you go to the rendered page, you can move around and play with the city. You can zoom in and see each individual building, and what they’re mostly made up of. Spoiler, most of them are all anonymous function, many levels deep.
This longer, lower city block is react.js
Things are much more spread out in this city, not as dense, but still it does quite a lot of stuff. React.js powers my photo/vacation site – steve.deadlycomputer.com. Take a look at the fully interactive version, it’s quite fun.