React Native is a JavaScript framework for writing real, natively rendering mobile applications for iOS and Android. It’s based on React, Facebook’s JavaScript library for building user interfaces, but instead of targeting the browser, it targets mobile platforms. In other words: web developers can now write mobile applications that look and feel truly “native,” all from the comfort of a JavaScript library that we already know and love. Plus, because most of the code you write can be shared between platforms, React Native makes it easy to simultaneously develop for both Android and iOS.

Similar to React for the Web, React Native applications are written using a mixture of JavaScript and XML-esque markup, known as JSX. Then, under the hood, the React Native “bridge” invokes the native rendering APIs in Objective-C (for iOS) or Java (for Android). Thus, your application will render using real mobile UI components, not webviews, and will look and feel like any other mobile application. React Native also exposes JavaScript interfaces for platform APIs, so your React Native apps can access platform features like the phone camera, or the user’s location.

React Native currently supports both iOS and Android, and has the potential to expand to future platforms as well. In this book, we’ll cover both iOS and Android. The vast majority of the code we write will be cross-platform. And yes: you can really use React Native to build production-ready mobile applications! Some anecdota: Facebook, Palantir, and TaskRabbit are already using it in production for user-facing applications.

If you are coming from a web background, the easiest way to get started with React Native is with Expo tools because they allow you to start a project without installing and configuring Xcode or Android Studio. Expo CLI sets up a development environment on your local machine and you can be writing a React Native app within minutes. For instant development, you can use Snack to try React Native out directly in your web browser.0

If you are familiar with native development, you will likely want to use React Native CLI. It requires Xcode or Android Studio to get started. If you already have one of these tools installed, you should be able to get up and running within a few minutes. If they are not installed, you should expect to spend about an hour installing and configuring them.

mport React, {Component} from 'react';
import {Text, View} from 'react-native';

class HelloReactNative extends Component {
  render() {
    return (
      <View>
        <Text>
          If you like React, you'll also like React Native.
        </Text>
        <Text>
          Instead of 'div' and 'span', you'll use native components
          like 'View' and 'Text'.
        </Text>
      </View>
    );
  }
}