I'm developing a Firefox add-on with which I want to use ECMAScript 6 features, but that's only available in the nightly builds. The nightly builds are sadly super slow and development suffers because of that.
Is there any way to use ECMAScript 6 for a Firefox add-on in combination with "jpm postwatch"?
Most ECMA6 features are already available in stable builds. Web content has to opt-in into some stuff, but that is not required from addons.
If you want to use ES6 features that are only available in nightly then that's because they're either new or unstable, it wouldn't make sense to test against stable anyway.
The nightly builds are sadly super slow and development suffers because of that.
It shouldn't, maybe that's the issue you need to fix.