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https://github.com/facebook/flow
Adds static typing to JavaScript to improve developer productivity and code quality.
https://github.com/facebook/flow
Last synced: about 14 hours ago
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Adds static typing to JavaScript to improve developer productivity and code quality.
- Host: GitHub
- URL: https://github.com/facebook/flow
- Owner: facebook
- License: mit
- Created: 2014-10-28T17:17:45.000Z (over 10 years ago)
- Default Branch: main
- Last Pushed: 2025-02-05T22:00:57.000Z (5 days ago)
- Last Synced: 2025-02-05T22:41:44.126Z (5 days ago)
- Language: OCaml
- Homepage: https://flow.org/
- Size: 136 MB
- Stars: 22,112
- Watchers: 386
- Forks: 1,864
- Open Issues: 964
-
Metadata Files:
- Readme: README.md
- Changelog: Changelog.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
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- stars - facebook/flow
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README
# Flow
Flow is a static typechecker for JavaScript. To find out more about Flow, check out [flow.org](https://flow.org/).
## Contents
- [Requirements](#requirements)
- [Using Flow](#using-flow)
- [Using Flow's parser from JavaScript](#using-flows-parser-from-javascript)
- [Building Flow from source](#building-flow-from-source)
- [Join the Flow community](#join-the-flow-community)
- [License](#license)
## Requirements
Flow works with:
* macOS (x86_64)
* Linux (x86_64 and arm64)
* Windows (x86_64, Windows 10 recommended)
There are [binary distributions](https://github.com/facebook/flow/releases) for each of these platforms and you can also build it from source on any of them as well.
## Using Flow
Check out the [installation instructions](https://flow.org/en/docs/install/), and then [the usage docs](https://flow.org/en/docs/usage/).
## Using Flow's parser from JavaScript
While Flow is written in OCaml, its parser is available as a compiled-to-JavaScript module published to npm, named [flow-parser](https://www.npmjs.com/package/flow-parser). **Most end users of Flow
will not need to use this parser directly**, but JavaScript packages which make use of parsing
Flow-typed JavaScript can use this to generate Flow's syntax tree with annotated types attached.
## Building Flow from source
Flow is written in OCaml (OCaml 5.2.0 is required).
1. Install system dependencies:
- Mac: `brew install opam`
- Debian: `sudo apt-get install opam`
- Other Linux: see [opam docs](https://opam.ocaml.org/doc/Install.html)
- Windows: [cygwin](https://cygwin.com/) and a number of dependencies like `make`, `gcc` and `g++` are required.
One way to install everything is to install [Chocolatey](https://chocolatey.org/) and then run `.\scripts\windows\install_deps.ps1` and `.\scripts\windows\install_opam.ps1`. Otherwise, see the "Manual Installation" section of [OCaml for Windows docs](https://fdopen.github.io/opam-repository-mingw/installation/) and install all of the packages listed in our `install_deps.ps1`.
The remainder of these instructions should be run inside the Cygwin shell: `C:\tools\cygwin\Cygwin`. Then `cd /cygdrive/c/Users/you/path/to/checkout`.
2. Validate the `opam` version is `2.x.x`:
```sh
opam --version
```
The following instructions expect `2.x.x`. Should your package manager have installed a `1.x.x` version, please refer to the [opam docs](https://opam.ocaml.org/doc/Install.html) to install a newer version manually.
3. Initialize `opam`:
```sh
# on Mac and Linux:
opam init
# on Windows:
scripts/windows/init_opam.sh
```
4. Install Flow's OCaml dependencies:
```sh
# from within this git checkout
make deps
```
**note**: If you find that you get an error looking for `ocaml-base-compiler` version, your local dependency repo may be out of date and you need to run `opam update` + `opam upgrade`
5. Build the `flow` binary:
```sh
eval $(opam env)
make
```
This produces the `bin/flow` binary.
6. Build `flow.js` (optional):
```sh
opam install -y js_of_ocaml.5.7.2
make js
```
This produces `bin/flow.js`.
The Flow parser can also be compiled to JavaScript. [Read how here](src/parser/README.md).
## Running the tests
To run the tests, first compile flow using `make`. Then run `bash ./runtests.sh bin/flow`
There is a `make test` target that compiles and runs tests.
To run a subset of the tests you can pass a second argument to the `runtests.sh` file.
For example: `bash runtests.sh bin/flow class | grep -v 'SKIP'`
## Join the Flow community
* Website: [https://flow.org](https://flow.org/)
* Discord: https://discord.gg/8ezwRUK
* irc: #flowtype on Freenode
* Twitter: follow [@flowtype](https://twitter.com/flowtype) and [#flowtype](https://twitter.com/hashtag/flowtype) to keep up with the latest Flow news.
* Stack Overflow: Ask a question with the [flowtype tag](https://stackoverflow.com/questions/tagged/flowtype)
## License
Flow is MIT-licensed ([LICENSE](https://github.com/facebook/flow/blob/main/LICENSE)). The [website](https://flow.org/) and [documentation](https://flow.org/en/docs/) are licensed under the Creative Commons Attribution 4.0 license ([website/LICENSE-DOCUMENTATION](https://github.com/facebook/flow/blob/main/website/LICENSE-DOCUMENTATION)).