ECMAScript Next refers to new features of the ECMA-262 standard (commonly referred to as JavaScript) introduced after ECMAScript 6 (ES2015). New versions of ECMAScript specifications are released yearly. This year, the ES2016 specification will be released and the ES2017 is the current ECMAScript draft specification.
You can see the latest proposals on the tc39/ecma262 GitHub repository.
A channel for feedback on ECMAScript standards is es-discuss.
ECMAScript 2016
These ES2016 / ES7 features are implemented:
Array.prototype.includes()(Firefox 43)TypedArray.prototype.includes()(Firefox 43)- Generators and generator methods are no longer constructable (Firefox 43)
- Proxy enumerate handler removed (Firefox 47)
- Exponentiation operator (Firefox Nightly, see bug 1243858 for remaining work)
String.prototype.padEnd()(Firefox 48)String.prototype.padStart()(Firefox 48)
ECMAScript 2017
These ES2017 / ES8 features are implemented:
Object.values()andObject.entries()(Firefox 47)Object.getOwnPropertyDescriptors()(Firefox 50)
Experimental new features
The following features are already implemented, but only available in the Firefox Nightly channel and not yet included in a draft edition of an ECMAScript specification.