Flow is a static typechecker for JavaScript. To find out more about Flow, check out flowtype.org.
For a background on the project, please read our launch blog post.
Flow works with:
There are binary distributions for Mac OS X and many variants of Linux; you can also build it from source on almost any 64-bit Linux variant.
Flow is written in OCaml (OCaml 4.01.0 or higher is required) and (on Linux) requires libelf. You can install OCaml on Mac OS X and Linux by following the instructions at ocaml.org.
Once you have these dependencies, building Flow just requires running
make
This produces a bin folder containing the flow binary.
Note: at this time, the OCaml dependency prevents us from adding Flow to npm. Try flow-bin if you need a npm binary wrapper.
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 'Skipping directory'
Flow is simple to install: all you need is the flow binary on your PATH and you're good to go.
You can also build and install flow via the OCaml OPAM package manager with one command:
opam install flowtype
If you don't have a new enough version of OCaml to compile Flow, you can also use OPAM to bootstrap a modern version. Install OPAM via the binary packages for your operating system and run:
opam init --comp=4.01.0 opam install flowtype eval `opam config env` flow --help
Check out http://flowtype.org for documentation and examples.
Flow is BSD-licensed. We also provide an additional patent grant.