Hermes

Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, simply enabling Hermes will result in improved start-up time, decreased memory usage and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
First, ensure you’re using at least version 0.60.2 of React Native. If you’re upgrading an existing app ensure everything works before trying to switch to Hermes.

https://github.com/facebook/hermes
https://facebook.github.io/react-native/docs/hermes

QuickJS Javascript Engine

News

  • 2019-07-09:

    • First public release

      Introduction

      QuickJS is a small and embeddable Javascript engine. It supports the ES2019 specification including modules, asynchronous generators and proxies.
      It optionally supports mathematical extensions such as big integers (BigInt), big floating point numbers (BigFloat) and operator overloading.
      Main Features:

  • Small and easily embeddable: just a few C files, no external dependency, 190 KiB of x86 code for a simple hello world program.

  • Fast interpreter with very low startup time: runs the 56000 tests of the ECMAScript Test Suite in about 100 seconds on a single core of a desktop PC. The complete life cycle of a runtime instance completes in less than 300 microseconds.
  • Almost complete ES2019 support including modules, asynchronous generators and full Annex B support (legacy web compatibility).
  • Passes 100% of the ECMAScript Test Suite.
  • Can compile Javascript sources to executables with no external dependency.
  • Garbage collection using reference counting (to reduce memory usage and have deterministic behavior) with cycle removal.
  • Mathematical extensions: BigInt, BigFloat, operator overloading, bigint mode, math mode.
  • Command line interpreter with contextual colorization implemented in Javascript.

  • Small built-in standard library with C library wrappers.

    Benchmark

    Online Demo

    An online demonstration of the QuickJS engine with its mathematical extensions is available at numcalc.com. It was compiled from C to WASM/asm.js with Emscripten.

    Documentation

    QuickJS documentation: HTML version, PDF version.
    Specification of the JS Bignum Extensions: HTML version, PDF version.

    Download

    QuickJS source code: quickjs-2019-07-09.tar.xz
    QuickJS complete tests: quickjs-tests-2019-07-09.tar.xz
    QuickJS unicode data (not needed unless you want to rebuild the unicode tables): quickjs-unicode-data-2019-07-09.tar.xz

    Sub-projects

    QuickJS embeds the following C libraries which can be used in other projects:

  • libregexp: small and fast regexp library fully compliant with the Javascript ES 2019 specification.

  • libunicode: small unicode library supporting case conversion, unicode normalization, unicode script queries, unicode general category queries and all unicode binary properties.
  • libbf: small library implementing arbitrary precision IEEE 754 floating point operations and transcendental functions with exact rounding. It is maintained as a separate project.

    Licensing

    QuickJS is released under the MIT license.
    Unless otherwise specified, the QuickJS sources are copyright Fabrice Bellard and Charlie Gordon.

Fabrice Bellard - https://bellard.org/

https://bellard.org/quickjs/