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

Promises provide a cleaner, more manageable approach to asynchronous programming with .then()/.catch() chaining and avoid 'callback hell,' while callbacks are the original async pattern in Node.js.

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

async/await is syntactic sugar over Promises, allowing developers to write asynchronous code that reads like synchronous code, making it easier to understand and debug.

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

Production applications should listen for the 'unhandledRejection' event on the process object to catch and log any Promise rejections that were not handled, preventing silent failures.

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

The error-first callback pattern is a Node.js convention where callback functions receive an error object as their first argument (null if successful) and results as subsequent arguments.

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

try...catch blocks around await expressions catch rejected Promises and thrown errors, providing a familiar synchronous error-handling pattern for asynchronous operations.

Node.js Practice Test

Node.js Practice Test

Node.js Async Patterns & Error Handling