CALLBACKFUNCTION

Callback Function in JavaScript

A callback function is a function that is passed as an argument to another function and is called later by that function.

Example:

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

callback();
}

function sayBye() {
console.log("Goodbye!");
}

greet("John", sayBye);


Output:

Hello John
Goodbye!

Why Do We Use Callback Functions?

Callbacks are useful when we want to say:

"After this task is completed, execute this function."

This is especially important in JavaScript because JavaScript frequently performs asynchronous operations.

For example:

*Waiting for a timer
*Getting data from a server
*Reading a file
*Handling a button click
*Processing events

Callback vs Normal Function

Normal function:

function add(a, b) {
return a + b;
}

console.log(add(10, 20));


We can directly calling the function.

Callback Function:

function calculate(a, b, callback) {
let result = a + b;
callback(result);
}

calculate(10, 20, function(result) {
console.log(result);
});

Here the function is passed to another function.