Flow
Learn how you can add Flow to your project as a dependency, ensure that Flow syntax is stripped from the compiled code, add type annotations, and run Flow to check them.
Setting up Flow
In contrast to React PropTypes, Flow is a static typechecker for JavaScript, not just for React components. Flow is also developed in-house at Facebook and thus integrates smoothly with most React setups. Up to version Babel 6, it even came pre-installed as part of the babelpreset-react and could be used without further setup.
Installation
Since Babel 7, Flow has been ported to its own Babel preset. To install it, you can run:
npm install @babel/preset-flow
Or, to install via Yarn:
yarn add @babel/preset-flow
Setting Babel preset
In addition to the installation step, you also have to manually set the @babel/preset-flow as a preset in the Babel config. Presets allow us to remove non-JavaScript syntax—in this case, Flow syntax—during the build ...