Callback Functions in JavaScript: A Comprehensive Guide

What is a Callback Function?

A callback function is a function passed as an argument to another function, to be executed after some operation completes.

Example

function greet(name, callback) {
    console.log("Hello " + name);
    callback();
}

greet("Alice", function() {
    console.log("Callback executed!");
});

Why Callbacks Matter

Callbacks are widely used for handling asynchronous operations like reading files, making API calls, or responding to events — allowing code to run only once a task finishes, without blocking the rest of the program.