# Step 1 — Check the Console Output

• Run your app in the terminal:

node app.js

• Look for:

  • Syntax errors

  • Exceptions (TypeError, ReferenceError, etc.)

  • Unhandled promise rejections

• Example crash message:

TypeError: Cannot read property 'name' of undefined
    at Object.<anonymous> (app.js:10:15)

• This tells you the file and line number causing the crash

## Step 2 — Enable Verbose Logging

• Add console logs to see what your app is doing:

console.log('Starting app...');
console.log('Data received:', data);

• Helps isolate the exact step where the crash occurs

## Step 3 — Wrap Code in Try/Catch

• Unhandled exceptions are a common crash cause

try {
  riskyFunction();
} catch (error) {
  console.error('Caught error:', error);
}

• For async functions:

async function fetchData() {
  try {
    const result = await fetchSomething();
  } catch (error) {
    console.error('Async error:', error);
  }
}

## Step 4 — Handle Unhandled Promise Rejections

• Node.js will crash for unhandled promise rejections in newer versions

process.on('unhandledRejection', (reason, promise) => {
  console.error('Unhandled Rejection:', reason);
});

• Logs the error and prevents silent crashes

## Step 5 — Check Memory Usage

• Apps crash due to memory leaks or out-of-memory errors

node --inspect app.js

• Monitor memory with Node.js inspector or Chrome DevTools → Memory tab

• Avoid storing large objects in memory indefinitely

## Step 6 — Use a Process Manager

• Use PM2 or forever to manage crashes:

npm install -g pm2
pm2 start app.js
pm2 logs
pm2 restart app

• Keeps your app running

• Shows crash logs for debugging

## Step 7 — Check Dependencies

• Outdated or incompatible packages can cause crashes

npm outdated
npm update

• Ensure package.json versions match your Node.js version

• Sometimes rolling back a package helps if an update broke something

## Step 8 — Isolate the Problem

• Comment out parts of your code or use minimal example

• Run step by step to see where it crashes

• Helps narrow down the cause without guessing

## Step 9 — Beginner-Friendly Checklist

## Step 10 — Conclusion

Node.js apps may crash for many reasons, but beginners can systematically debug by:

• Reading console and log output carefully

• Adding try/catch blocks and handling promise rejections

• Checking memory usage and dependencies

• Using a process manager to monitor and restart the app

Following these steps ensures you can find the root cause and make your Node.js application stable.