The Complete ECMAScript 2015-2019 Guide

ECMAScript is the standard upon which JavaScript is based, and it's often abbreviated to ES. Discover everything about ECMAScript and its latest features

• What is TC39
• ES Versions
• ES Next

Whenever you read about JavaScript you’ll inevitably see one of these terms:

• ES3
• ES5
• ES6
• ES7
• ES8
• ES2015
• ES2016
• ES2017
• ECMAScript 2015
• ECMAScript 2016
• ECMAScript 2017
• ECMAScript 2018
• ECMAScript 2019

What do they mean?

They are all referring to a standard, called ECMAScript.

ECMAScript is the standard upon which JavaScript is based, and it’s often abbreviated to ES.

Beside JavaScript, other languages implement(ed) ECMAScript, including:

• ActionScript (the Flash scripting language), which is losing popularity since Flash will be officially discontinued in 2020
• JScript (the Microsoft scripting dialect), since at the time JavaScript was supported only by Netscape and the browser wars were at their peak, Microsoft had to build its own version for Internet Explorer

but of course JavaScript is the most popular and widely used implementation of ES.

Why this weird name? Ecma International is a Swiss standards association who is in charge of defining international standards.

When JavaScript was created, it was presented by Netscape and Sun Microsystems to Ecma and they gave it the name ECMA-262 alias ECMAScript.

This press release by Netscape and Sun Microsystems (the maker of Java) might help figure out the name choice, which might include legal and branding issues by Microsoft which was in the committee, according to Wikipedia.

After IE9, Microsoft stopped branding its ES support in browsers as JScript and started calling it JavaScript (at least, I could not find references to it any more)

So as of 201x, the only popular language supporting the ECMAScript spec is JavaScript.

What is TC39

TC39 is the committee that evolves JavaScript.

The members of TC39 are companies involved in JavaScript and browser vendors, including Mozilla, Google, Facebook, Apple, Microsoft, Intel, PayPal, SalesForce and others.

Every standard version proposal must go through various stages, which are explained here.

ES Versions

I found it puzzling why sometimes an ES version is referenced by edition number and sometimes by year, and I am confused by the year by chance being -1 on the number, which adds to the general confusion around JS/ES 😄

Before ES2015, ECMAScript specifications were commonly called by their edition. So ES5 is the official name for the ECMAScript specification update published in 2009.

Why does this happen? During the process that led to ES2015, the name was changed from ES6 to ES2015, but since this was done late, people still referenced it as ES6.

This table should clear things a bit:

ES Next

ES.Next is a name that always indicates the next version of JavaScript.

So at the time of writing, ES2019 has been released, and ES.Next is ES2020