Before discussing ES5 or ES6 let’s discuss what actually is ECMAScript-
In a similar way, HTML specifications (most recently HTML5) are defined by the organising body and are implemented by the browser vendors. Different browsers implement specifications in different ways, and there’s varying amounts of support for different features.
We can view the all latest specification at-
ECMAScript – http://www.ecma-international.org/default.htm
ES2015 or ES6 – http://www.ecma-international.org/ecma-262/6.0/
ECMA Proposals- https://github.com/tc39/proposals