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TC39 - ECMAScript

Scope - Programme of work

Upcoming meetings

TC39 has bi-monthly face to face meetings, usually in California (the Bay area). In addition, at least one meeting is held in Redmond, WA (July meeting usually). Attendance at meetings is controlled by Ecma-International by-laws and rules. Visitors on a one-time basis are usually approved by the Secretary General and requests should be directed to him for approval.

Next meetings

  • 25-27 July 2017 (at Microsoft in Redmond)
  • 26-28 September 2017 (at Bocoup in Boston)
  • 28-30 November 2017 (at Airbnb in San Francisco)


A presentation "ECMAScript overview" by J. Neumann, TC39 Chairman, is available here. The audio file is available here.

ECMAScript™ is the scripting language that is used to create web pages with dynamic behavior. ECMAScript™, which is more commonly known by the name JavaScript™, is an essential component of every web browser and the ECMAScript™ standard is one of the core standards that enable the existence of interoperable web applications on the World Wide Web.

The ECMAScript™ specification has been developed by Ecma TC39 whose membership includes all major browser vendors. The candidate milestone designates that the authoring process was  completed, followed by a testing and validation phase of the project where TC39 members create and test implementations of the candidate specification to verify its correctness and the feasibility of creating interoperable implementations. The test implementations will also be used for web compatibility testing to ensure that the revised specification remains compatible with existing web applications. TC39 has  committed to participating in this testing process. A test262 archive webpage is available here.

Current work on ECMAScript™

Work on future ECMAScript™ editions continues as part of the previously announced ECMAScript™ "Harmony" project. More details of the current work on ECMAScript "Harmony" are described on this Wiki. A sixth edition of the standard is currently under development with a target date of June 2015 for completion. The latest version of the draft is available here.

Latest version of ECMAScript™

The ECMAScript™, Standard ECMA-262 sixth edition is publicly available from the Ecma International website.

The latest drafts are available at: Reporters should generally only file bugs if the bug is still present in the latest drafts.

Please find hereafter the place to file bugs:

Earlier versions of ECMAScript™ (available here)

The ECMAScript™, Standard ECMA-262 Edition 5.1 (identical with ISO/IEC 16262 third Edition), is publicly available from the Ecma International web site. A comparable test suite known as Test262 (ES5) has been developed and approved as ECMA TR/104.

The revision of ECMA-262 known as ECMAScript™, fifth Edition was approved in December, 2009. It was previously developed under the working name ECMAScript™ 3.1. The fifth Edition codifies de facto interpretations of the language specification that have become common among browser implementations and adds support for new features that have emerged since the publication of the third Edition. Such features include accessor properties, reflective creation and inspection of objects, program control of property attributes, additional array manipulation functions, support for the JSON object encoding format, and a strict mode that provides enhanced error checking and program security.

Testing of the fifth Edition was completed by mid-July 2009. Technical errors and ambiguities were resolved during this process, and a final draft of the specification was agreed upon in September for submission to the Ecma General Assembly for final approval in December 2009.   This has resulted in a fast-track submission and ballot within ISO/IEC JTC 1 for revision of ISO/IEC 16262.

An earlier major revision of the ECMAScript™ standard was the third Edition, published in 1999 (a Russian translation of ECMA-262 3rd edition is available here). After completion of the third Edition, significant work was done to develop a fourth Edition. Although development of a fourth Edition was not completed, that work influenced ECMAScript™, fifth Edition and is continuing to influence the ongoing development of ECMAScript™.


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