How to fix FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory in Node.js

# Set heap size to 4GB (4096 MB)
node --max-old-space-size=4096 app.js

# For npm scripts, add to package.json
"scripts": {
  "start": "node --max-old-space-size=4096 server.js",
  "build": "node --max-old-space-size=4096 node_modules/.bin/webpack"
}

# Linux/macOS
export NODE_OPTIONS="--max-old-space-size=4096"
npm run build

# Windows (PowerShell)
$env:NODE_OPTIONS="--max-old-space-size=4096"
npm run build

# Windows (cmd)
set NODE_OPTIONS=--max-old-space-size=4096 && npm run build

export NODE_OPTIONS="--max-old-space-size=4096"

ENV NODE_OPTIONS="--max-old-space-size=4096"

NODE_OPTIONS=--max-old-space-size=4096

# Run with inspector enabled
node --inspect app.js

# Or with explicit memory monitoring
node --inspect --trace-gc app.js

npm install -g clinic
clinic doctor -- node app.js

// Bad: loads entire file into memory
const data = fs.readFileSync('large-file.json', 'utf8');
const json = JSON.parse(data);

// Good: streams data in chunks
const stream = fs.createReadStream('large-file.json');
const parser = JSONStream.parse('*');
stream.pipe(parser);
parser.on('data', (chunk) => {
  // Process each chunk
});

// Bad: loads all records
const allRecords = await db.users.findMany();

// Good: processes in batches
const pageSize = 100;
let page = 0;
while (true) {
  const records = await db.users.findMany({
    skip: page * pageSize,
    take: pageSize
  });
  if (records.length === 0) break;
  // Process records
  page++;
}

// Use WeakMap for automatic garbage collection
const cache = new WeakMap();

// Explicitly null out large objects when done
largeObject = null;

// Bad: event listener never removed
eventEmitter.on('data', handler);

// Good: remove when done
eventEmitter.on('data', handler);
// Later...
eventEmitter.removeListener('data', handler);

// Better: use once() for single-use listeners
eventEmitter.once('data', handler);

// Clear intervals and timeouts
const interval = setInterval(() => {}, 1000);
// Later...
clearInterval(interval);

// Use AbortController for cleanup
const controller = new AbortController();
eventEmitter.on('data', handler, { signal: controller.signal });
// Later...
controller.abort(); // Removes all listeners

// Bad: creates circular reference
const obj1 = {};
const obj2 = { ref: obj1 };
obj1.ref = obj2; // Circular reference

// Good: avoid or break circular references
obj1.ref = null; // Break the cycle when done

module.exports = {
  mode: 'production',
  optimization: {
    minimize: true,
    usedExports: true, // Tree shaking
    splitChunks: {
      chunks: 'all', // Split large bundles
      cacheGroups: {
        vendor: {
          test: /[\\/]node_modules[\\/]/,
          name: 'vendors',
          chunks: 'all'
        }
      }
    }
  },
  // Reduce memory usage during builds
  stats: 'errors-only',
  performance: {
    hints: false
  }
};

export default {
  build: {
    rollupOptions: {
      output: {
        manualChunks(id) {
          if (id.includes('node_modules')) {
            return 'vendor';
          }
        }
      }
    }
  }
};