It is maintained by the TC39 committee.
Some key things to note:
- The latest version is ECMAScript 2023, defined at https://tc39.es/ecma262/2023/
- New versions are released annually by TC39 to evolve the language over time.
- Features at different stages of the proposal process can be found at https://tc39.es/process-document/
- The GitHub repo for ongoing development is
Go look at the source code.