In June 2004, Ecma International published ECMA-357 standard, defining an extension to ECMAScript, known as
ECMAScript for XML (E4X). Ecma also defined a "Compact Profile" for ECMAScript – known as ES-CP, or ECMA 327 – that was designed for resource-constrained devices, which was withdrawn in 2015.
4th edition (abandoned) The proposed 4th edition of ECMA-262 (
ECMAScript 4 or
ES4) would have been the first major update to ECMAScript since the 3rd edition was published in 1999. The specification (along with a reference implementation) was originally targeted for completion by October 2008. The first draft was dated February 1999. An overview of the language was released by the working group on 23 October 2007. By August 2008, the ECMAScript 4th edition proposal had been scaled back into a project code named
ECMAScript Harmony. Features under discussion for Harmony at the time included: •
classes, •
a module system, • optional
type annotations and
static typing, probably using a
structural type system, •
generators and
iterators, •
destructuring assignment, and •
algebraic data types. The intent of these features was partly to better support
programming in the large, and to allow sacrificing some of the script's ability to be dynamic to improve performance. For example,
Tamarin – the virtual machine for ActionScript, developed and open-sourced by Adobe – has
just-in-time compilation (JIT) support for certain classes of scripts. In addition to introducing new features, some ES3 bugs were proposed to be fixed in edition 4. These fixes and others, and support for
JSON encoding/decoding, have been folded into the ECMAScript, 5th Edition specification. Work started on Edition 4 after the ES-CP (Compact Profile) specification was completed, and continued for approximately 18 months where slow progress was made balancing the theory of Netscape's JavaScript 2 specification with the implementation experience of Microsoft's
JScript .NET. After some time, the focus shifted to the
ECMAScript for XML (E4X) standard. The update has not been without controversy. In late 2007, a debate between Eich, later the
Mozilla Foundation's CTO, and Chris Wilson,
Microsoft's platform architect for
Internet Explorer, became public on a number of
blogs. Wilson cautioned that because the proposed changes to ECMAScript made it backwards incompatible in some respects to earlier versions of the language, the update amounted to "breaking the Web", and that stakeholders who opposed the changes were being "hidden from view". Eich responded by stating that Wilson seemed to be "repeating falsehoods in blogs" and denied that there was attempt to suppress dissent and challenged critics to give specific examples of incompatibility. He pointed out that
Microsoft Silverlight and
Adobe AIR rely on
C# and
ActionScript 3 respectively, both of which are larger and more complex than ECMAScript Edition 3.
5th edition – ECMAScript 2009 Yahoo, Microsoft, Google, and other 4th edition dissenters formed their own subcommittee to design a less ambitious update of ECMAScript 3, tentatively named ECMAScript 3.1. This edition would focus on security and library updates, with a large emphasis on compatibility. After the aforementioned public sparring, the ECMAScript 3.1 and ECMAScript 4 teams agreed on a compromise: the two editions would be worked on, in parallel, with coordination between the teams to ensure that ECMAScript 3.1 remains a strict subset of ECMAScript 4 in both semantics and syntax. However, the differing philosophies in each team resulted in repeated breakages of the subset rule, and it remained doubtful that the ECMAScript 4 dissenters would ever support or implement ECMAScript 4 in the future. After over a year since the disagreement over the future of ECMAScript within the Ecma Technical Committee 39, the two teams reached a new compromise in July 2008:
Brendan Eich announced that Ecma TC39 would focus work on the ECMAScript 3.1 (later renamed to ECMAScript, 5th Edition) project with full collaboration of all parties, and vendors would target at least two interoperable implementations by early 2009. In April 2009, Ecma TC39 published the "final" draft of the 5th edition and announced that testing of interoperable implementations was expected to be completed by mid-July. On 3 December 2009, ECMA-262 5th edition was published. Additions include
JSON, String.trim() to easily remove whitespaces surrounding a string (" example " to "example"), String.charAt() to return a single character from a given position in a string, and Array.isArray(). A comma after the final pair of values in an object (var example = { "property1":"value1", "property2":"value2", }) also no longer causes a syntax error.
6th edition – ECMAScript 2015 The 6th edition, ECMAScript 6 (
ES6) and later renamed to ECMAScript 2015, was finalized in June 2015. This update adds significant new syntax for writing complex applications, including class declarations (class Foo { ... } ), ES6 modules like import * as moduleName from "..."; export const Foo, but defines them semantically in the same terms as ECMAScript 5 strict mode. Other new features include iterators and for...of loops,
Python-style generators, arrow function expression (() => {...} ), let keyword for local declarations, const keyword for constant local declarations, binary data, typed arrays, new collections (maps, sets and WeakMap),
promises, number and math enhancements, reflection, proxies (metaprogramming for virtual objects and wrappers) and
template literals using backticks (`) for multi-line strings without
escape characters. The complete list is extensive. As the first "ECMAScript Harmony" specification, it is also known as "ES6 Harmony".
7th edition – ECMAScript 2016 The 7th edition, or ECMAScript 2016, was finalized in June 2016. Its features include exponentiation operator ** for numbers, await, async keywords for asynchronous programming (as a preparation for ES2017), and the function. Its features include the , and functions for easy manipulation of Objects, async / await constructions that use generators and promises, and additional features for concurrency and
atomics. It also includes String.prototype.padStart(). New features include the spread operator and rest parameters (...) for object literals, asynchronous iteration, Promise.prototype.finally and additions to RegExp. Added features include, but are not limited to, Array.prototype.flat, Array.prototype.flatMap, changes to Array.sort, and Object.fromEntries.
11th edition – ECMAScript 2020 The 11th edition, or ECMAScript 2020, was published in June 2020. In addition to new functions, this version introduces a BigInt primitive type for arbitrary-sized integers, the
nullish coalescing operator, and the
globalThis object. This version introduces the toSorted, toReversed, with, findLast, and findLastIndex methods on Array.prototype and TypedArray.prototype, as well as the toSpliced method on Array.prototype; added support for #!
shebang comments at the beginning of files to better facilitate executable ECMAScript files; and allowed the use of most Symbols as keys in weak collections.
15th edition – ECMAScript 2024 The 15th edition, ECMAScript 2024, was published in June 2024. This version introduces the Object.groupBy and Map.groupBy static methods, Promise.withResolvers, various set operations on Set.prototype, and the /v unicode flag for regular expressions. The Object.groupBy and Map.groupBy methods group an iterable collection using the return value of a provided callback function. // sample data const arr = [ { year: "2024", id: 0 }, { year: "2023", id: 1 }, { year: "2024", id: 2 }, ]; const obj = Object.groupBy(arr, (el) => el.year); console.log(obj); // { "2024": [{ year: "2024", id: 0 }, { year: "2024", id: 2 }], "2023": [{ year: "2023", id: 1 }] } Promise.withResolvers provides a simple way to get a promise's resolve and reject functions directly without having to assign them in the constructor. // ES 2023 let resolve; let reject; let promise = new Promise((res, rej) => { resolve = res; reject = rej; }); // ES 2024 const { resolve, reject, promise } = Promise.withResolvers(); The /v flag in regular expressions is simply an improved version of the /u flag, but as it makes backwards-incompatible changes it had to be introduced as a new flag.
16th edition – ECMAScript 2025 The 16th edition of ECMAScript released in 2025. It adds the following: • The object which can wrap iterators like and provides a functional interface with
lazy evaluation. • : call a method which may or may not be a promise as a promise • New methods: , , , , , • function to escape a string so it can be concatenated together with a regex pattern. • Importing JSON files directly as modules • Float16Array along with related TypedArray methods
ES.Next ES.Next is a dynamic name that refers to whatever the next version is at the time of writing. ES.Next features include finished proposals (aka "stage 4 proposals") as listed at finished proposals that are not part of a ratified specification. The language committee follows a "living spec" model, so these changes are part of the standard, and ratification is a formality. ==References==