Javascript formally releases once a year, but individual feature adoption in browsers is totally separate from that, and happens.... whenever they feel like it. v8 (chrome's js engine) doesn't have a set release schedule, but has already had 6 formal minor releases this year, each partially adopting some new JS runtime features, all of which have already shipped to chrome.
At our current pace, we formally release 4 times a year, for reference, which is actually a far cry from the more continuous deployment browser vendors currently have setup.
The main difference is that most people kinda ignore new JavaScript stuff for awhile until it trends or gains sufficient rollout. It's an interesting world - I can't really say that people are actually JavaScript version aware, beyond, maybe, what compatibility presets @babel/preset-env gives them.
We actually primarily use StackOverflow for this (as it's the first resource many devs go to, as you did, and it's collaborative). We even pre-seed questions and answers for releases, sometimes.
If you find an answer on SO is out of date - suggest a new answer (or ask for one) and get it updated (there's far, far too many for us to keep explicit track of them, there's only a handful of us on the team)! :D
JavaScript itself keeps changing, so we need to keep pace with that, for one. Beyond that, we relentlessly seek to improve how people interact with our editor tools, and make additions to the (type) language and compiler to support that. .d.ts files from js files, for example, are highly motivated by a desire to better support incremental compilations with .js inputs, as .d.ts files are used as incremental metadata. Assertion signatures were added to better express the cross-call control flow patterns some (assertion) libraries already use, to make using them in a well-typed way more ergonomic.
Generally speaking, it's not often we add something that _invalidates_ the old way to do something (in the language) - our additions are usually made to make new patterns possible to express.
At our current pace, we formally release 4 times a year, for reference, which is actually a far cry from the more continuous deployment browser vendors currently have setup.
The main difference is that most people kinda ignore new JavaScript stuff for awhile until it trends or gains sufficient rollout. It's an interesting world - I can't really say that people are actually JavaScript version aware, beyond, maybe, what compatibility presets @babel/preset-env gives them.