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JavaScript

JavaScript Callbacks

JavaScript callbacks pass functions into other functions as arguments.

Read Time

5 min read

Difficulty

Beginner

Last Updated

Jun 15, 2026

Version

v1.0.0

Introduction

JavaScript functions act like regular data, meaning you can pass one function into another. The receiving function will run the callback function later. Developers use this for actions that take time, like waiting for a file to load.

Example

1/* this uses a callback */
2function sayHello() {
3  console.log("Hello!");
4}
5
6setTimeout(sayHello, 3000); // Runs after 3 seconds

Key Points

A callback is a function passed as an argument.
Callbacks control the execution order of asynchronous code.
Using too many nested callbacks creates "callback hell".
Modern JavaScript prefers Promises over callbacks.

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