Node.js Async Patterns & Error Handling

Question 1

What is the difference between Promises and callbacks in Node.js?

Accepted Answer

Promises provide a cleaner syntax for handling async operations and support chaining; callbacks are the older pattern

Answer

There is no difference; they are interchangeable

Answer

Callbacks are newer and more efficient than Promises

Answer

Promises can only handle synchronous operations

Question 2

What does 'async/await' provide in Node.js?

Accepted Answer

Syntactic sugar over Promises that makes asynchronous code look and behave like synchronous code

Answer

A way to make synchronous code run asynchronously automatically

Answer

A method to block the event loop until an operation completes

Answer

A replacement for the event loop entirely

Question 3

How should unhandled Promise rejections be handled in a production Node.js application?

Accepted Answer

By adding a global 'unhandledRejection' event handler and logging the error

Answer

By ignoring them since Node.js handles them automatically

Answer

By wrapping every line of code in try-catch blocks

Answer

By disabling Promises entirely in production

Question 4

What is the 'error-first callback' pattern in Node.js?

Accepted Answer

A convention where callbacks receive an error object as the first argument, null if no error occurred

Answer

A pattern where errors are always thrown as exceptions

Answer

A method of logging errors to a file before callbacks execute

Answer

A pattern where the first callback in a chain handles all errors

Question 5

What is the purpose of 'try...catch' with async/await?

Accepted Answer

To catch errors thrown by awaited Promises in a synchronous-looking style

Answer

To try different API endpoints until one works

Answer

To cache the results of async operations

Answer

To prevent the event loop from processing errors

Question 6

What happens if an error is thrown inside an async function without a try/catch?

Accepted Answer

The returned Promise is rejected with the thrown error

Answer

The application crashes immediately

Answer

The error is silently ignored

Answer

Node.js automatically retries the function