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ECMAScript Features

QuickJS-ng aims to support the latest available ECMAScript features once they hit the spec. The project focuses on delivering state-of-the-art JavaScript features, typically once they are stable (stage 4) but sometimes even at earlier stages.

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Feature Support

QuickJS-ng includes support for a wide range of modern ECMAScript features:

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Data Structures

  • Resizable ArrayBuffer - Dynamic buffer resizing capabilities
  • Float16Array - 16-bit floating point typed arrays
  • WeakRef - Weak references to objects
  • FinalizationRegistry - Cleanup callbacks when objects are garbage collected
  • Set operations - Mathematical set operations

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Language Features

  • Iterator Helpers - Convenient methods for working with iterators
  • Promise.try - Synchronous function wrapping in promises
  • Error.isError - Check if a value is an Error object

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Non-Standard APIs

Some non-standard but widely used APIs have also been added for compatibility:
  • V8’s Stack Trace API
    • Error.captureStackTrace
    • Error.prepareStackTrace
    • Error.stackTraceLimit

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Test262 Compliance

Progress on Test262 compliance can be tracked at:

Test262 Compliance Dashboard

View real-time compliance status for QuickJS-ng on Test262.fyi

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Limitations

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Internationalization (Intl)

Due to size constraints, it is unlikely QuickJS will ever support the Intl APIs. The Intl specification is large and would significantly increase the engine’s footprint, which goes against QuickJS-ng’s goal of being small and embeddable.

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ECMAScript Specification

QuickJS-ng targets the latest ECMAScript specification published by TC39. New features are typically added soon after reaching stage 4 in the TC39 process.

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