Error Handling

What is Error Handling?

Error handling is the process of anticipating, detecting, and responding to errors in your code. Proper error handling prevents your application from crashing and provides useful feedback.

try...catch

The try...catch statement allows you to handle errors gracefully.

try {
  // Code that might throw an error
  let result = riskyOperation();
  console.log(result);
} catch (error) {
  // Code to handle the error
  console.error("Something went wrong:", error.message);
}

The throw Statement

Use throw to create custom errors.

function divide(a, b) {
  if (b === 0) {
    throw new Error("Division by zero is not allowed");
  }
  return a / b;
}

try {
  divide(10, 0);
} catch (error) {
  console.error(error.message);
}

The finally Block

Code in finally always runs, regardless of whether an error occurred.

try {
  // Risky code
} catch (error) {
  // Handle error
} finally {
  // Always runs (cleanup, close connections, etc.)
}

Custom Error Types

class ValidationError extends Error {
  constructor(message) {
    super(message);
    this.name = "ValidationError";
  }
}

function validateUser(user) {
  if (!user.name) {
    throw new ValidationError("Name is required");
  }
}

Common Mistakes

• Using try...catch everywhere (only use where errors are expected)
• Swallowing errors without logging or handling them
• Using catch without checking the error type
• Throwing non-Error objects (always use new Error())

Quick Quiz

Summary

• try...catch handles errors gracefully
• throw creates custom errors
• finally runs regardless of errors
• Create custom error types by extending Error
• Don't swallow errors — log them
• Check error types before handling