SpiderMonkey and Mozilla as a whole have a mission-based commitment to implement draft standards, so to the extent that we have prototyped Proxies, WeakMaps, generators, let, and other extensions now approved for "ES.next", the module has influence. Upstream of it is the Ecma TC39 process, about which I spoke recently:
There are a number of influential people on the committee. It's a committee, the economics make this inevitable. But we have pretty good core group of people who work on the standard and try to serve JS as a programming language, not as a techno-political bargaining chip or mere means to a business-agenda end.
This is, somewhat surprisingly, not true, especially if you're just considering the language proper. There are about 15 people who are regular members of the committee, and some of them end up having a big influence.
Brendan is a prime example; his language design taste and leadership matter a lot. There are certainly other examples. Dave Herman, also at Mozilla, has been the lead on a whole host of things, from extending iterators and generators to the design of the new module system, which I worked on as well. Tom Van Cutsem and Mark Miller created the Proxy system.
Outside of pure JS, the designers of WebGL/Typed Arrays and WebWorkers have both had big impacts.
Ultimately, even on a committee, individual people can make a big impact.
Thanks, Brendan.