Ecma International approved the 17th edition of the ECMAScript language standard, ECMAScript 2026, on June 30. The additions are small and useful: Array.fromAsync for turning an async iterable into an array, Error.isError for a reliable check that something is an error object across realms, base64 and hex conversion on Uint8Array, Math.sumPrecise for summing floats without the usual drift, Iterator.concat for joining iterators, and the getOrInsert and getOrInsertComputed upserts on Map and WeakMap.
The question for a team is never whether a feature is in the standard. It is whether the feature is in the runtimes you ship to, and whether it makes code easier to read for the next person. Those are the two tests I use when deciding what a style guide allows.
By those tests, I would allow Array.fromAsync and Error.isError immediately, with a polyfill where the browser matrix requires one, because both replace patterns that were ugly and subtly wrong. The Uint8Array conversions replace hand-rolled base64 code that almost every codebase has and nobody trusts. Math.sumPrecise is for the one place in the codebase that adds up money or measurements, and that place should use it.
What I would not do is let the whole edition in on the day of approval. A style guide is a statement about what the team has agreed to recognize on sight, and that takes a deliberate decision per feature, not a version bump.
How does your team decide when a new language feature is allowed in?
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