recipe-04-adding-flow.md

Adding Flow

Note: This is outdated now that jetpack uses swc-loader instead of babel.

Flow is a static type checker that helps you write code with fewer bugs. Check out this introduction to using static types in JavaScript if you are new to this concept.

To add Flow to a jetpack project, follow these steps:

1. Run npm install --save-dev flow-bin @babel/preset-flow.
2. Run npx flow init to create a [.flowconfig file].
3. Add // @flow to any files you want to type check (for example, to src/App.js).
4. Create .babelrc with the following contents

{
  "presets": [
    "@babel/preset-flow"
  ]
}

Now you can run npx flow to check the files for type errors or run npx jetpack to run your app as usual.

To learn more about Flow, check out its documentation.