Not sure what you mean by &quot;lining up with&quot;? The development of ES6&#x2F;ES2015, and the development of all the browsers and their various JS engines are pretty much ongoing, all the time.<p>The Edge, Chrome, Firefox and WebKit teams are all working on ES6 compatibility, and releasing new versions pretty frequently. The Edge team are in the lead because they&#x27;ve implemented more features, faster.<p>Chrome&#x2F;V8 was actually quite a way behind for a while, although they&#x27;ve caught up quite a bit recently. I believe the situation wrt to V8 within Google was a bit messy for a while, as the original developers (Lars Bak, etc.) were more interested in championing Dart than implementing the latest ES6 features. Eventually, Google had to create a new team, based in Munich, to work on V8.