Ecma International's TC39 is a group of JavaScript developers, implementers, academics, and more, collaborating with the community to maintain and evolve the definition of JavaScript.

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TC39 welcomes contributions from the JavaScript community, whether it is feedback on existing proposals, improved documentation, testing, implementations, or even language feature ideas. See our contributor guide for details.

To participate in TC39 meetings as a member, join Ecma.


We develop the JavaScript (formally, ECMAScript) specification on GitHub and meet every two months to discuss proposals. To learn more about the process, please take a look at the five stages for new language feature proposals. See our meeting agendas and minutes to learn more.

State of Proposals

Current Candidates for the Specification

This section features proposals that are in Stage 3 of our process, which means they are close to completion.

How to read the proposals list

Each proposal has links out to other resources. The tags identify the following attributes. Below you will find a table with example tags and their meanings. All tags have hover text if you need help getting oriented.

Types of tags and what they mean


Authors and Champions: Philipp Dunkel, Maggie Johnson-Pint, Matt Johnson-Pint, Brian Terlson, Shane Carr, Ujjwal Sharma, Philip Chimento, Jason Williams, Justin Grant
Provides standard objects and functions for working with dates and times.

Change Array by Copy

Authors and Champions: Ashley Claymore, Robin Ricard
Provides additional methods on Array.prototype and TypedArray.prototype to enable changes on the array by returning a new copy of it with the change.


Authors: Caridy Patiño, Jean-Francois Paradis | Champions: Dave Herman, Mark Miller, Caridy Patiño, Leo Balter, Rick Waldron, Chengzhong Wu
ECMAScript Proposal, specs, and reference implementation for Realms

Intl Locale Info

Authors and Champions: Frank Yung-Fong Tang
An API to expose information of locale, such as week data ( first day of a week, weekend start, weekend end), hour cycle, measurement system, commonly used calendar, etc.

Symbols as WeakMap keys

Authors and Champions: Daniel Ehrenberg, Richard Button, Robin Ricard, Leo Balter, Rick Waldron, Caridy Patiño
Permit Symbols as keys in WeakMaps, entries in WeakSets and WeakRefs, and registered in FinalizationRegistries
See proposals in all stages