Brendan may not be helming JavaScript anymore. But he was very active during critical standardization period. For example:
2009: https://www.youtube.com/watch?v=eUtsgUrF-ec
2011: https://brendaneich.com/2011/08/my-txjs-talk-twitter-remix/
2012: https://brendaneich.com/2012/10/harmony-of-dreams-come-true/
Also note that Asm.js (2013 precursor to WebAssembly) was developed during his term at Mozilla.