function sum(num1,num2,callback){

    let total = num1 + num2

    callback(total)

}

​

sum(10,20,function(total){

    // received total here

    console.log(total);

})

​

sum(5,16,(total)=>{

    console.log(total);

})

/*

A callback function is a function passed into another function

as an argument, which is then invoked inside the outer function

to complete some kind of routine or action. 

*/

function greeting(name) {

  alert('Hello ' + name);

}

​

function processUserInput(callback) {

  var name = prompt('Please enter your name.');

  callback(name);

}

​

processUserInput(greeting);

// The above example is a synchronous callback, as it is executed immediately.

document.querySelector('video').playbackRate = 1.5

function greeting(name) {

  alert('Hello ' + name);

}

​

function processUserInput(callback) {

  var name = prompt('Please enter your name.');

  callback(name);

}

​

processUserInput(greeting);

// What is callback functions in js

​

// Lets make a function

​

// Putting parameter in it "callback"

function func1(callback) {

  console.log(callback); // Log 'callback'; And now our parameter callback is a function and we can call it from our func1 and this is what callback is

  hello();

}

​

// Making one more function to print hello world in console

function hello() {

  console.log("Hello world");

}

​

func1(hello); // Call func and give hello function as a arguement; Yes we can give function as arguement

​

// func1(hello()); // This is wrong way to give function as arguement

document.querySelector('video').playbackRate = 2.5

function greeting(name) {

  alert('Hello ' + name);

}

​

function processUserInput(callback , {

  var name = prompt('Please enter your name.');

  callback(name);

}}

​

processUserInput(greeting);

// A callback function is a function that is passed as an argument to another function 

// and is expected to be called back (executed) at a certain point within the containing function.

// It allows you to define an action to be taken after a certain task or event has been completed.

​

// Example of a callback function

function sayHello(name, callback) {

  console.log('Hello, ' + name);

  callback();

}

​

function sayGoodbye() {

  console.log('Goodbye!');

}

​

sayHello('John', sayGoodbye);

// A function that accepts a callback function as an argument

function performTask(callback) {

  // Simulating an asynchronous task

  setTimeout(function() {

    // Perform some task

    console.log('Task completed');

​

    // Execute the callback function

    callback();

  }, 2000);

}

​

// Define the callback function

function afterTaskCompletion() {

  console.log('Callback function executed');

}

​

// Call the performTask() function and pass the callback

performTask(afterTaskCompletion);

// Example using callback in JavaScript

function greetUser(name, callback) {

  console.log("Hello, " + name);

  callback();

}

​

function finishGreeting() {

  console.log("Greeting finished.");

}

​

// Usage

greetUser("John", finishGreeting);