The Road to ECMAScript 6

In 2007, JavaScript was at a crossroads. The popularity of Ajax was ushering in a new age of dynamic web applications, while JavaScript hadn’t changed since the third edition of ECMA-262 was published in 1999. TC-39, the committee responsible for driving the ECMAScript development process, put together a large draft specification for ECMAScript 4. ECMAScript 4 was massive in scope, introducing changes both small and large to the language. Updated features included new syntax, modules, classes, classical inheritance, private object members, optional type annotations, and more.

The scope of the ECMAScript 4 changes caused a rift to form in TC-39, with some members feeling that the fourth edition was trying to accomplish too much. A group of leaders from Yahoo, Google, and Microsoft created an alternate proposal for the next version of ECMAScript that they initially called ECMAScript 3.1. The “3.1” was intended to show that this was an incremental change to the existing standard.

ECMAScript 3.1 introduced very few syntax changes, instead focusing on property attributes, native JSON support, and adding methods to already-existing objects. Although there was an early attempt to reconcile ECMAScript 3.1 and ECMAScript 4, this ultimately failed as the two camps had difficulty with the very different perspectives on how the language should grow.

In 2008, Brendan Eich, the creator of JavaScript, announced that TC-39 would focus its efforts on standardizing ECMAScript 3.1. They would table the major syntax and feature changes of ECMAScript 4 until after the next version of ECMAScript was standardized, and all members of the committee would work to bring the best pieces of ECMAScript 3.1 and 4 together after that point into an effort initially nicknamed ECMAScript Harmony.

ECMAScript 3.1 was eventually standardized as the fifth edition of ECMA-262, also described as ECMAScript 5. The committee never released an ECMAScript 4 standard to avoid confusion with the now-defunct effort of the same name. Work then began on ECMAScript Harmony, with ECMAScript 6 being the first standard released in this new “harmonious” spirit.

ECMAScript 6 reached feature complete status in 2015 and was formally dubbed “ECMAScript 2015.” (But this text still refers to it as ECMAScript 6, the name most familiar to developers.) The features vary widely from completely new objects and patterns to syntax changes to new methods on existing objects. The exciting thing about ECMAScript 6 is that all of its changes are geared toward solving problems that developers actually face.