I ran all 324 historical and active ECMAScript proposals through TypeSafe AI's System One model (Jev) and Jev-like models to classify where each idea came from and score it on domain shape, adoption path, cognitive load, web-compatibility risk, and runtime changes.
In this talk, we look at thirty years of language design through that dataset to uncover where JavaScript features actually originate, the seven buckets every proposal falls into, and the surprising patterns that decide whether an idea becomes new syntax or a standard library API. You will walk away with a clear mental model of how language ideas are born in TC39, alongside a live explorer to query any JavaScript proposal yourself.
This talk has been presented at JSNation US 2026, check out the latest edition of this JavaScript Conference.
















