What are the types of errors in Node.js? | Node.js Interview Questions

What You'll Learn

Types of errors in Node.js
How to handle each type
Best practices

Error Types

1. Standard JavaScript Errors

code.jsJavaScript

// SyntaxError, TypeError, ReferenceError, RangeError
throw new TypeError('Expected string');
throw new RangeError('Index out of bounds');

2. System Errors

code.jsJavaScript

// OS-level errors
const fs = require('fs');

fs.readFile('/nonexistent', (err, data) => {
  if (err) {
    console.log(err.code);    // 'ENOENT'
    console.log(err.syscall); // 'open'
    console.log(err.path);    // '/nonexistent'
  }
});

Common system error codes:

ENOENT - File/directory not found
EACCES - Permission denied
ECONNREFUSED - Connection refused
ETIMEDOUT - Operation timed out

3. Custom Application Errors

code.jsJavaScript

class AppError extends Error {
  constructor(message, statusCode) {
    super(message);
    this.statusCode = statusCode;
    this.isOperational = true;
    Error.captureStackTrace(this, this.constructor);
  }
}

class NotFoundError extends AppError {
  constructor(message = 'Resource not found') {
    super(message, 404);
  }
}

// Usage
throw new NotFoundError('User not found');

Handling Uncaught Errors

code.jsJavaScript

// Uncaught exceptions
process.on('uncaughtException', (err) => {
  console.error('Uncaught:', err);
  process.exit(1);
});

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