Atom Shell and ES6 Harmony

When building an application using the Atom Shell, you may want to take advantage of newer Javascript features from ES6 (Harmony) like arrow functions, generators, for ... of loops and many other things which are not enabled in the V8 Javascript engine by default.

Fortunately, enabling this is pretty easy!

app.on('ready', function() {
  app.commandLine.appendSwitch('js-flags', '--harmony');
  ...
}

When starting up your Atom Shell application, you can append switches to the command line that will be given to the embedded Chromium browser engine.

Note that if you have an incorrect flag being passed, the other flags that you set may be ignored, so keep an eye on this as you update to newer versions of Atom Shell as the valid flags may have changed.

Unfortunately, it can be confusing figuring out which version of V8 is being used and what ES6 features are available. As of the time of this writing, Atom Shell 0.18.1 is using a Chromium 38 and so it falls in between the Chromium 37 and 39 columns on this compatibility chart. (But don't look at the Node Harmony column for figuring out what Atom Shell supports!)