Installing and initializing Flow

Before you can start implementing type-safe React components, you need to install and initialize Flow. I'll show you how this is done with a create-react-app environment, but the same steps can be followed for almost any React environment.

You can install Flow globally, but I would recommend installing it locally, along with all the other packages that your project depends on. Unless there's a good reason to install something globally, install it locally. This way, anyone installing your application can get every dependency by running npm install.

To install Flow locally, run the following command:

npm install flow-bin --save-dev

This will install the Flow executable locally to your project and will update your package.json so that Flow is installed as a dependency of your project. Now let's add a new command to package.json so that you can run the Flow type checker against your source code. Make the scripts section look like this:

"scripts": { 
  "start": "react...