ECMAScript Support
Jint implements modern ECMAScript directly from the specification and validates behavior against test262.
Editions
The engine supports language features through ECMAScript 2025, including modules, async functions, generators, typed arrays, BigInt, private fields, top-level await, iterator helpers, explicit resource management, and Temporal.
Selected proposals are also available before they receive an edition number. Proposal APIs can change as their specifications evolve.
Current proposal-stage features include decorators, explicit resource management, immutable ArrayBuffer, import bytes, iterator chunking and sequencing, JSON parse source text access, Math.sumPrecise, ShadowRealm, Temporal, Uint8Array base64 conversion, and upsert operations. Jint follows each proposal's current specification rather than treating proposal behavior as a frozen contract.
Runtime differences
ECMAScript does not define browser or Node.js globals. Jint therefore installs neither by default:
- enable standards-based runtime APIs through Web APIs;
- enable supported Node modules through Node compatibility;
- use
Jint.Browserwhen scripts require a document and DOM.
Measured conformance
At the pinned test262 commit, Jint passes 102,585 of 102,692 generated cases (99.9%). The run covers annexB, built-ins, intl402, language, and staging; 107 generated cases are skipped.
This percentage describes the configured corpus, not every file in test262. The active pin and the reasons for each exclusion are recorded in Test262Harness.settings.json.