JavaScript Callback Function

A callback function is a function passed as an argument to another function, which is executed after the parent function completes. Callbacks can be synchronous or asynchronous.

What is a Callback Function?

• A function passed to another function as an argument.
• Called after the parent function finishes execution.
• Can be synchronous or asynchronous.

Example 1: Basic Callback Function

Example 2: Callback with setTimeout (Asynchronous)

Example 3: Custom Asynchronous Callback

Why Use Callbacks?

• Execute code after async tasks finish.
• Write non-blocking code.
• Common in event handling, file reading, HTTP requests.

Callback Hell (Downside)

Callbacks can be nested deeply, making code hard to read and maintain.

Solution: Use Promises or async/await for cleaner code.

Named vs Anonymous Callbacks

• Named Callback:

• Anonymous Callback:

Key Takeaways

• Callbacks are functions passed and called later.
• Useful in async programming with events, timers, API calls.
• Help modularize and reuse code.
• Avoid callback hell by using Promises or async/await.
• Callbacks can be synchronous or asynchronous.