Building SpiderMonkey is not hard at all today: https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Build_Documentation https://developer.moz

Building SpiderMonkey is not hard at all today: https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Build_Documentation https://developer.mozilla.org/en-US/docs/Mozilla/Projects/Sp... The only issue is that you have to clone whole mozilla-central even if you only work with small part of it. But once you pull it, the building and hacking on it is quite easy :)