React Native Academy · Lesson

Installing Node, Expo CLI, and Simulators

Set up Node.js, the Expo CLI, and configure iOS Simulator or Android Emulator so you can run React Native apps locally.

Installing Node, Expo CLI, and Simulators is a free React Native Academy lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the React Native Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why Node.js Powers React Native

React Native runs on Node.js — it powers the Metro bundler that turns your JSX into an app. Install the LTS version for stability, ideally via the nvm version manager.

# Install nvm (Node Version Manager)
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash

# Then install the latest LTS Node
nvm install --lts
nvm use --lts

# Verify installation
node --version   # e.g. v20.12.0
npm --version    # e.g. 10.5.0

Installing the Expo CLI

The Expo CLI lets you create, run, and build apps without touching native code. Pair it with the Expo Go app to scan a QR code and see your app on a real phone instantly.

# Install Expo CLI globally
npm install -g expo-cli

# Verify the installation
expo --version

# Alternatively, use npx (no global install needed)
npx create-expo-app --version

Setting Up iOS Simulator on macOS

For the iOS Simulator you need a Mac with Xcode installed. Open Xcode once to accept its license, then add the command line tools. Expo can launch a simulator with one keypress.

# Install Xcode Command Line Tools
xcode-select --install

# Open a simulator from the terminal
open -a Simulator

# List available simulator devices
xcrun simctl list devices

Setting Up Android Emulator

For Android you need Android Studio. Install the SDK and emulator, create a virtual Pixel device, and set the ANDROID_HOME variable so Expo can find everything. See the code.

# Add to ~/.zshrc or ~/.bashrc
export ANDROID_HOME=$HOME/Library/Android/sdk
export PATH=$PATH:$ANDROID_HOME/emulator
export PATH=$PATH:$ANDROID_HOME/platform-tools

# Reload shell config
source ~/.zshrc

# Verify adb is found
adb --version

Understanding the Metro Bundler

Starting a project launches Metro, the bundler that watches your files and reloads instantly with Fast Refresh. If things get stale, clear its cache with the --clear flag.

# Start Metro and clear cache
npx expo start --clear

# Metro outputs a QR code and key shortcuts:
#  i → open iOS Simulator
#  a → open Android Emulator
#  r → reload the app
#  m → toggle the developer menu

Java Development Kit for Android

Android builds need a Java Development Kit — Expo recommends JDK 17. Install it, then run java --version to confirm it's on your PATH. The code installs it via Homebrew.

# Install JDK 17 via Homebrew (macOS)
brew install --cask temurin@17

# Verify Java version
java --version
# Expected: openjdk 17.x.x

# On Windows: download installer from
# https://adoptium.net/temurin/releases/

Verifying Your Full Setup

Once everything's installed, run npx expo-env-info (or react-native doctor) to scan your setup. It flags anything missing, so fix those issues before your first project.

# Check your environment with Expo
npx expo-env-info

# Or use the React Native community CLI doctor
npx react-native doctor

# Install Watchman for better file watching (macOS)
brew install watchman

Watchman: Faster File Watching

Watchman is a file-watcher from Facebook that makes Metro detect changes much faster, especially on macOS. Install it via Homebrew before you start building.

# Install Watchman on macOS
brew install watchman

# Verify installation
watchman version

# If Metro has stale Watchman state, reset it
watchman watch-del-all

Environment Variables and PATH

Many setup headaches come down to a missing PATH entry — your shell can't find adb or the emulator. Add the paths to ~/.zshrc, then reload it. The code shows exactly what.

# Example ~/.zshrc additions for React Native
export JAVA_HOME=$(/usr/libexec/java_home -v 17)
export ANDROID_HOME=$HOME/Library/Android/sdk
export PATH=$PATH:$ANDROID_HOME/emulator
export PATH=$PATH:$ANDROID_HOME/tools
export PATH=$PATH:$ANDROID_HOME/tools/bin
export PATH=$PATH:$ANDROID_HOME/platform-tools

# Apply changes
source ~/.zshrc

Expo Go App on a Real Device

The fastest way to test on a real phone is the Expo Go app. Run expo start, then scan the QR code, and your app loads over Wi-Fi. Perfect for quick development. 📱

# Start Expo development server
npx expo start

# Expo prints a QR code in the terminal.
# Scan it with:
#   iOS: Camera app → tap the banner
#   Android: Expo Go app → Scan QR Code

# Or press 's' to switch to Expo Go mode
# if using a dev build by default

Troubleshooting Common Setup Issues

Most setup snags are predictable: a busy port 8081, a stale Metro cache, the wrong Node version, or a missing ANDROID_HOME. And always read the red error screen carefully.

# Common fixes

# Clear Metro cache
npx expo start --clear

# Kill process on port 8081
lsof -ti:8081 | xargs kill -9

# Check connected Android devices
adb devices

# Restart adb server if devices not showing
adb kill-server
adb start-server

Quick Check

Test your understanding of React Native Mobile Development concepts from this lesson.

Lesson Recap

You built your toolchain: Node and nvm run the JavaScript, Expo CLI scaffolds and serves your app, and Watchman plus the SDKs power simulators. Next: your first project! 🎉

Frequently asked questions

Is the “Installing Node, Expo CLI, and Simulators” lesson free?

Yes — the full text of “Installing Node, Expo CLI, and Simulators” is free to read here on the web, and the React Native Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the React Native Academy course, upgrade to CoddyKit PRO.

What will I learn in “Installing Node, Expo CLI, and Simulators”?

Set up Node.js, the Expo CLI, and configure iOS Simulator or Android Emulator so you can run React Native apps locally. You practise React Native Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start React Native Academy?

No prior experience is required. React Native Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Installing Node, Expo CLI, and Simulators” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this React Native Academy lesson?

Yes. Every React Native Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

Installing Node, Expo CLI, and Simulators
Creating Your First Expo Project
Running on Device and Emulator
Understanding the Project Structure

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