Front-end Frameworks

Hermes – JavaScript engine optimized for React Native

Hermes is a JavaScript engine optimized for fast start-up of React Native apps.

For many apps, 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,

This is free and open source software.

Features include:

  • Ahead-of-time static optimization – build-time precompilation of JavaScript into efficient bytecode.
  • Optimized for mobile – small in APK size, lean on memory, and starts instantly.
  • Easy integration – implements JavaScript standards.
  • Compact bytecode.
  • Supports ECMAScript 2015 (ES6):
    • Symbols (including most well-known Symbols).
    • Iteration (with [Symbol.iterator]).
    • for..of loops.
    • Array spread.
    • Object rest/spread.
    • Shorthand property and computed property on object literals.
    • Destructuring assignment (with array and object “rest” properties).
    • Template string literals.
    • Generators (function* and yield).
    • TypedArrays.
    • Arrow functions.
    • Optional chaining and nullish coalescing (?. and ??).
    • Reflection (Reflect and Proxy).
    • Intl, or Internationalization APIs – currently Android only
    • ES6 Promise.
    • All ES6 JS library functions
      • Set/Map.
      • WeakSet/WeakMap.
      • ES6 String searching functions.
      • ES6 Array searching functions.

Support: GitHub Code Repository
Developer: Facebook, Inc. and its affiliates
License: MIT License

Hermes is written in C++. Learn C++ with our recommended free books and free tutorials.

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