Worth a look imho:
This is a guided tour of what it is like to work on the SpiderMonkey compiler and improve conformance with ECMA-262, the JavaScript Specification. In this series, we go step by step through open issues, understand spec text, and implement fixes. Viewers will be invited to ask questions, make suggestions, and, if they fix a bug themselves, have their solutions discussed on the stream.
https://developer.mozilla.com/events/compiler-compiler-yulia-startsev/