React Native is a popular Javascript framework that builds on top of React by using native components to create a real mobile app indistinguishable from one made using Xcode or Android Studio. The main difference with native development is that you get to use CSS, hot-reload, Javascript and other familiar techniques that the Web has grown over the past decades. Most importantly, you're building for both iOS and Android using the same codebase.
Before starting, you'll need the Node package manager (NPM) for installing React and Expo. To install Node, you need to head to their site and download the version appropriate to your system. You can also install node using Homebrew (Mac only) if you prefer.
If you're on a Mac, I highly recommend installing Xcode for the required Command Line Tools and for using the iOS Simulator. Xcode also comes with Git, which is wonderful for development.
Expo will allow us to have a development environment for creating our app. Go to Terminal and type this command and press Enter.
sudo npm install expo-cli --global
Go to their Quick Start guide for more detailed instructions.
Go to your new project's folder and start the environment.
expo start
npm install