v8 did and then pulled support. JSC (javascript core) added support in June/July 2016 (a year and a half ago). Their team makes some great points about this. h

v8 did and then pulled support. JSC (javascript core) added support in June/July 2016 (a year and a half ago). Their team makes some great points about this. https://github.com/tc39/ecma262/issues/535 https://github.com/tc39/ecma262/issues/535 https://github.com/rwaldron/tc39-notes/blob/master/es7/2016-05/may-24.md#syntactic-tail-calls-bt https://github.com/rwaldron/tc39-notes/blob/master/es7/2016-... For all of Google's talk about their syntactic tail call proposal, they haven't cared enough to implement it -- only to remove their PTC code. FF and MS are in the same position. At this point, I don't really care one way or the other, they need to quit the excuses, quit the petty power struggles, and do something one way or the other. Every year they wait is another year before we can use it. EDIT: I'd also add that the performance impact in the real world seems to be close to zero. https://github.com/tc39/proposal-ptc-syntax/issues/7 https://github.com/tc39/proposal-ptc-syntax/issues/7