Ecma International Approves ECMAScript 2026, the 17th Edition of the JavaScript Standard, With Seven Finished Proposals

Ecma International approved ECMAScript 2026 on June 30. The 17th edition of the JavaScript standard adds Math.sumPrecise, Iterator.concat, Array.fromAsync, Error.isError, Map upsert methods, Uint8Array base64 and hex conversion, and JSON.parse source access.

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Editor's Note · July 9, 2026

Clarification:

The article places three phrases inside quotation marks and attributes them to InfoWorld, but each is lightly compressed rather than reproduced verbatim. It quotes Math.sumPrecise as "for summing numbers while minimizing precision loss"; InfoWorld's exact wording is "for summing an iterable of numbers of varying magnitude while minimizing precision loss." The meaning is unchanged.

Clarification:

The article quotes Array.fromAsync as "for constructing arrays from async sources"; InfoWorld's exact wording is "for constructing arrays from async iterables and other async sources." The meaning is unchanged.

Clarification:

The article quotes the JSON.parse addition as a parameter enabling revivers "to access matched JSON source segments"; InfoWorld's exact wording is "a parameter to JSON.parse revivers to access the matched segment of JSON source." The meaning is unchanged.

Overview

Ecma International has approved ECMAScript 2026, the 17th edition of the JavaScript programming language specification, according to InfoWorld. The standards organization approved the specification on June 30. The release notes on the ecma262 repository confirm the two-step process behind the final text: “TC39 approved this in March 2026; Ecma approved it on June 30th, 2026.” A candidate specification had been frozen on March 31, pending approval by the Ecma GA. The timing mirrors last year’s cycle, when Ecma approved ECMAScript 2025 on June 25, 2025, per the same releases page.

What We Know

Seven finished proposals make up the edition. The TC39 finished-proposals table lists seven proposals with an expected publication year of 2026: Upsert, JSON.parse source text access, Iterator Sequencing, Uint8Array to/from Base64, Math.sumPrecise, Error.isError, and Array.fromAsync.

New built-ins for math, iteration, and errors. According to InfoWorld, the edition adds Math.sumPrecise “for summing numbers while minimizing precision loss”; Iterator.concat “for sequencing iterators”; Array.fromAsync “for constructing arrays from async sources”; and Error.isError “for identifying error objects.”

Map and WeakMap gain upsert methods. The proposal-upsert repository documents four new methods — Map.prototype.getOrInsert, Map.prototype.getOrInsertComputed, and their WeakMap.prototype counterparts. The methods “return the value associated with key if it is already present in the Map or WeakMap, and otherwise insert the key with the provided default value, or the result of calling a provided callback function, and then return that value.”

Standard base64 and hex conversion for binary data. The proposal-arraybuffer-base64 repository lists six methods: Uint8Array.prototype.toBase64 and Uint8Array.prototype.toHex for encoding, Uint8Array.fromBase64 and Uint8Array.fromHex for decoding into new arrays, and Uint8Array.prototype.setFromBase64 and Uint8Array.prototype.setFromHex for writing decoded data into an existing array. The set-style methods return “a { read, written } pair,” and decoding throws on improperly encoded input, per the proposal README.

Finer-grained JSON handling. InfoWorld reports that the edition adds a parameter enabling JSON.parse revivers “to access matched JSON source segments,” along with JSON.rawJSON “for fine control over JSON.stringify output for primitive values.”

Some of these features took years to land. The meeting-notes trails in the finished-proposals table show Error.isError, championed by Jordan Harband, was first discussed in committee in March 2016; the Upsert proposal, championed by Daniel Minor, traces back to October 2019 and only cleared Stage 4 at the committee’s January 2026 meeting; and Array.fromAsync, championed by J.S. Choi, dates to August 2021. Kevin Gibbons championed both Math.sumPrecise and the Uint8Array base64 work, Michael Ficarra championed Iterator Sequencing, and Richard Gibson championed JSON.parse source text access, per the same table.

What Is Not in This Edition

RegExp.escape carries a 2025 expected publication year in the finished-proposals table — it shipped with the previous edition. Three already-finished proposals are marked for 2027 instead: Temporal, Explicit Resource Management, and Joint Iteration. Temporal, the replacement for JavaScript’s Date object, reached Stage 4 in March 2026 and was among the most anticipated additions in Node.js 26, as previously reported.

What We Don’t Know

The cited sources do not describe the implementation status of each ES2026 feature across JavaScript engines and runtimes.
Beyond the three finished proposals already marked with a 2027 expected publication year, the sources do not indicate what else may make the ECMAScript 2027 cutoff.