The General Assembly of Ecma International has announced the approval of ECMA-262 6th edition, which is the Language Specification of ECMAScript 6 (ES6), also known as ECMAScript 2015.
ECMAScript 5 was standardized in late 2009 but only recently has it has started showing up in browsers. It supersedes the 3rd edition, which was ratified in 1999. ECMAScript 5 is actually two languages, ES5/Default and ES5/Strict. Future versions are going to be built on top of ES5/Strict and it is recommended that the default version be avoided.