Callback pattern and callback hell in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a callback function in Node.js?

A callback function is a function passed as an argument to another function, which is then called after some operation completes. It helps handle asynchronous tasks.

beginner

Explain the term 'callback hell'.

Callback hell happens when many callbacks are nested inside each other, making code hard to read and maintain, like a pyramid or 'arrow' shape.

intermediate

Why does callback hell make code difficult to maintain?

Because deeply nested callbacks create complex, hard-to-follow code flow, making debugging and updates confusing and error-prone.

intermediate

How can you avoid callback hell in Node.js?

You can avoid callback hell by using techniques like named functions, Promises, async/await, or modularizing code into smaller functions.

beginner

Show a simple example of a callback function in Node.js.

Example:
function greet(name, callback) {
  console.log('Hello ' + name);
  callback();
}
greet('Alice', () => {
  console.log('Greeting done');
});

What is the main purpose of a callback function in Node.js?

A To stop the program execution

B To handle asynchronous operations after they complete

C To create global variables

D To style the webpage

Callbacks let you run code after an asynchronous task finishes, like reading a file or fetching data.

What does 'callback hell' usually look like in code?

A Using only synchronous code

B A single function with no callbacks

C Functions without any parameters

D Many nested callback functions inside each other

Callback hell is when callbacks are nested deeply, making code hard to read.

Which of these is NOT a way to avoid callback hell?

A Using Promises

B Using async/await

C Writing all code in one big callback

D Breaking code into smaller functions

Writing all code in one big callback causes callback hell, not avoids it.

In the callback pattern, when is the callback function called?

A After the main task finishes

B Before the main task starts

C Only if an error occurs

D Randomly during execution

The callback runs after the main asynchronous task completes.

What is a common problem caused by callback hell?

A Code becomes hard to read and debug

B Code runs faster

C More memory is freed

D Functions stop working

Callback hell makes code complex and difficult to maintain.

Describe what a callback function is and why it is used in Node.js.

Think about how Node.js waits for tasks like reading files.

Explain what callback hell is and list two ways to avoid it.

Imagine a pyramid of functions inside functions.