Spidermonkey compares very well with V8: http://arewefastyet.com/ http://arewefastyet.com/ (beats it in Sunspider, is roughly equal in others) And it maintain

Spidermonkey compares very well with V8: http://arewefastyet.com/ http://arewefastyet.com/ (beats it in Sunspider, is roughly equal in others) And it maintains the lead in ECMAScript6 support: https://kangax.github.io/compat-table/es6/ https://kangax.github.io/compat-table/es6/