Ask HN: Good JavaScript codebases to read?

While it might bring a few boos or hisses these days, there are a lot of lessons to be learned from reading the jQuery code base.

I'd personally love to see a frontend-heavy codebase that is using relatively new tooling (for example, ES2015 with Babel, React on a significant scale, etc.) if anyone would like to share :).

Derek recommends Backbone and Underscore - at least they can be found nicely annotated here:

https://sivers.org/learn-js

http://underscorejs.org/docs/underscore.html

http://backbonejs.org/docs/backbone.html

I'd start with the repos for the libraries/framework(s) you've been using lately. Or for something a little different, take a look at Babel's codebase (https://github.com/babel/babel).