I would be interested in some spec test suite coverage figures. I have used a few js engines in the past (nashorn, rhino, otto) and all had problems with missin

I would be interested in some spec test suite coverage figures. I have used a few js engines in the past (nashorn, rhino, otto) and all had problems with missing edge cases in the APIs or really weird quirks in the interop with the host environment. https://github.com/tc39/test262 https://github.com/tc39/test262 is the ecma test suite. rhino for example has extensive gaps: https://github.com/mozilla/rhino/blob/master/testsrc/test262.properties https://github.com/mozilla/rhino/blob/master/testsrc/test262... It is really frustrating that in the end, there aren't really that many actually compliant implementations. Especially implementing the exact regex behaviour. EDIT: apparently this exists, at least partially: https://kangax.github.io/compat-table/es6/ https://kangax.github.io/compat-table/es6/ The smaller engines are missing however.