There are many browsers but there is only a handset of rendering engines and these are the base for all browsers. This is of course good to keep in mind when testing for browser compability.
These are the main rendering engines used today:
EcmaScript 5.1 (ES5) was a main update that was released in 2011 that enhanced
JavsScript in many ways. I'm using the added
Array functions all
the time and getters/setters are used in the data binding implementation.
Object.create is used easily implement proper inheritance and
Object.keys makes it possible to list the properties of an object.
EcmaScript Edition 6 (ES6), also called Harmony was released in June 2015. es6-features.org provides a good summary of the new features. Implementation of Harmony is far from complete in all browsers. These features must be used with care for some time to come. You can use Traceur iframe you want to start using ES6 already now.
Features for EcmaScript 7 were
listed already before EcmaScript 6 was apporved. One feature I'm looking forward
Object.observe. It will make data-binding a breeze.