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.
Key Features
- 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.
Website: hermesengine.dev
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.
Related Software
| JavaScript Engines | |
|---|---|
| V8 | High-performance JavaScript and WebAssembly engine |
| SpiderMonkey | JavaScript and WebAssembly Engine, used in Firefox, Servo and more |
| QuickJS | Small and embeddable Javascript engine |
| Hermes | JavaScript engine optimized for React Native |
| JerryScript | JavaScript engine for the Internet of Things |
| Duktape | Embeddable JavaScript engine, focusing on portability and compact footprint |
| Elk | Tiny embeddable JavaScript engine |
Read our verdict in the software roundup.
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