Here you can find lots of resources for learning React.
Resources are project based and cover all of the main topics to help you start as fast as possible.
From lesson 09 - http requests onwards, in some lessons, you will start using Firebase API.
You will need to create Firebase project and import provided learning-react-data.json file in realtime database.
Then, in lessons where you see .env.example file, create .env file at the root of the project and assign your API key to a variable with name REACT_APP_API_KEY.
