How to Run React Native App: Step-by-Step Guide

To run a React Native app, first install dependencies with npm install or yarn. Then start the Metro bundler using npx react-native start and run the app on Android with npx react-native run-android or on iOS with npx react-native run-ios.

Syntax

Here are the main commands to run a React Native app:

• npm install or yarn: Installs project dependencies.
• npx react-native start: Starts the Metro bundler, which serves your JavaScript code.
• npx react-native run-android: Builds and runs the app on an Android device or emulator.
• npx react-native run-ios: Builds and runs the app on an iOS simulator (macOS only).

Make sure you have an Android emulator or iOS simulator running, or a physical device connected.

bash

npm install
npx react-native start
npx react-native run-android
# or
npx react-native run-ios

Example

This example shows how to run a simple React Native app on Android:

1. Open a terminal in your project folder.
2. Run npm install to install dependencies.
3. Start the Metro bundler with npx react-native start.
4. Open another terminal and run npx react-native run-android.
5. The app will build and launch on your connected Android device or emulator.

javascript

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

export default function App() {
  return (
    <View style={{flex:1, justifyContent:'center', alignItems:'center'}}>
      <Text>Hello, React Native!</Text>
    </View>
  );
}

Output

A mobile screen with centered text: "Hello, React Native!"

Common Pitfalls

Common mistakes when running React Native apps include:

• Not starting the Metro bundler before running the app.
• Trying to run iOS commands on non-macOS systems.
• Not having an emulator or device connected.
• Missing Android SDK or Xcode setup.
• Using outdated React Native CLI commands.

Always check your environment setup and device connections before running.

bash

Wrong:
npx react-native run-ios  # on Windows or Linux

Right:
# Use Android commands on Windows/Linux
npx react-native run-android

# Use iOS commands only on macOS
npx react-native run-ios

Quick Reference

Command	Purpose
npm install or yarn	Install project dependencies
npx react-native start	Start Metro bundler
npx react-native run-android	Run app on Android device/emulator
npx react-native run-ios	Run app on iOS simulator (macOS only)

Key Takeaways

Always install dependencies before running your React Native app.

Start the Metro bundler with 'npx react-native start' before launching the app.

Use 'npx react-native run-android' for Android and 'npx react-native run-ios' for iOS (macOS only).

Ensure your device or emulator/simulator is running and connected.

Avoid running iOS commands on non-macOS systems to prevent errors.