Skip to content

/ hermes

Hermes is a small and lightweight JavaScript engine optimized for running React Native on Android.
C++ JavaScript Python Java CMake Shell Other
  1. C++ 74.7%
  2. JavaScript 20.9%
  3. Python 2.1%
  4. Java 1.0%
  5. CMake 0.8%
  6. Shell 0.2%
  7. Other 0.3%
Branch: master
Find file
Clone or download

Clone with HTTPS

Use Git or checkout with SVN using the web URL.

Open in Desktop Download ZIP

Latest commit

@avp @facebook-github-bot
avp and facebook-github-bot Attempt to avoid compiler timeouts in test262. 
Reviewed By: dulinriley

Differential Revision: D22012521

fbshipit-source-id: ef74d8de2bfe69d5f370a08d8e62121c9bd1efc8
Latest commit eae5142 Jun 19, 2020

Files

Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
.circleci Bundle vcruntime140_1.dll in NPMs (#269) Jun 9, 2020
API Fix buffer prefix used in error msg Jun 16, 2020
android Include JSI headers in the Android build May 20, 2020
cmake/modules Improve build and add instructions Feb 21, 2020
config Tidy up license headers [1/2] Oct 15, 2019
doc Update ReactNativeIntegration.md Jun 8, 2020
external Add missing cstdint include. Jun 5, 2020
first-party Expose function to determine if a global JVM is available May 28, 2020
include Check SymbolID in CheckHeapWellFormedAcceptor Jun 19, 2020
lib Check SymbolID in CheckHeapWellFormedAcceptor Jun 19, 2020
lldb Make chaos_until_crash.py script for use with Mozilla RR chaos mode Apr 16, 2020
npm Bundle vcruntime140_1.dll in NPMs (#269) Jun 9, 2020
public Add a flag for optimized eval Jun 15, 2020
test Validate regex flags at compile time Jun 15, 2020
tools Restore runtime flag validation and unbump bytecode version Jun 16, 2020
unittests Check SymbolID in CheckHeapWellFormedAcceptor Jun 19, 2020
utils Attempt to avoid compiler timeouts in test262. Jun 19, 2020
website Improve playground UX on mobile OS May 26, 2020
.clang-format Initial commit Jul 10, 2019
.clang-tidy Initial commit Jul 10, 2019
.gitignore BUCK build to use external/llvh Feb 9, 2020
CMakeLists.txt Add support for OSS-Fuzz build May 21, 2020
CODE_OF_CONDUCT.md Update Code of Conduct Sep 5, 2019
CONTRIBUTING.md Initial commit Jul 10, 2019
LICENSE Initial commit Jul 10, 2019
README.md Update gramatical mistake README.md (#124) Apr 2, 2020
git-revision Initial commit Jul 10, 2019

README.md

Hermes JS Engine

MIT license npm version PRs Welcome Hermes logo - large H with wings

Hermes is a JavaScript engine optimized for fast start-up of React Native apps on Android. It features ahead-of-time static optimization and compact bytecode.

If you're only interested in using pre-built Hermes in a new or existing React Native app, you do not need to follow this guide or have direct access to the Hermes source. Instead, just follow these instructions to enable Hermes.

If you want to know how to build and hack on Hermes directly, and/or integrate Hermes built from source into a React Native app then read on.

The instructions here very briefly cover steps to build the Hermes CLI. They assume you have typical native development tools setup for your OS, and support for cmake and Ninja. For more details of required dependencies, building Hermes with different options, etc. follow these links instead:

To build a local debug version of the Hermes CLI tools the following steps should get you started on macOS/Linux:

mkdir hermes_workingdir
cd hermes_workingdir
git clone https://github.com/facebook/hermes.git
hermes/utils/build/configure.py
cd build
ninja

Or if you're using Windows, the following should get you going in a Git Bash shell:

mkdir hermes_workingdir
cd hermes_workingdir
git -c core.autocrlf=false clone https://github.com/facebook/hermes.git
hermes/utils/build/configure.py --build-system='Visual Studio 16 2019' --cmake-flags='-A x64 --distribute
cd build
MSBuild.exe ALL_BUILD.vcxproj /p:Configuration=Release

You will now be in a directory with the output of building Hermes into CLI tools. From here you can run a piece of JavaScript as follows:

echo "'use strict'; function hello() { print('Hello World'); } hello();" | ./bin/hermes

Contributing

The main purpose of this repository is to continue to evolve Hermes, making it faster and more efficient. We are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving Hermes.

Code of Conduct

Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.

Contributing Guide

Read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to Hermes.

License

Hermes is MIT licensed.

You can’t perform that action at this time.