example of callback function in javascript

Example 1: javascript callback

/*
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.

Example 2: callback function js

function greeting(name) {
  alert('Hello ' + name);
}

function processUserInput(callback) {
  var name = prompt('Please enter your name.');
  callback(name);
}

processUserInput(greeting);

Example 3: what are callback functions

// A function which accepts another function as an argument
// (and will automatically invoke that function when it completes - note that there is no explicit call to callbackFunction)
funct printANumber(int number, funct callbackFunction) {
    printout("The number you provided is: " + number);
}

// a function which we will use in a driver function as a callback function
funct printFinishMessage() {
    printout("I have finished printing numbers.");
}

// Driver method
funct event() {
   printANumber(6, printFinishMessage);
}

Example 4: javascript callback

// Create a callback in the probs, in this case we call it 'callback'
function newCallback(callback) {
  callback('This can be any value you want to return')
}

// Do something with callback (in this case, we console log it)
function actionAferCallback (callbackData) {
  console.log(callbackData)
}

// Function that asks for a callback from the newCallback function, then parses the value to actionAferCallback
function requestCallback() {
  newCallback(actionAferCallback)
}

Example 5: javascript callback function

const message = function() {  
    console.log("This message is shown after 3 seconds");
}
 
setTimeout(message, 3000);

Example 6: js callback function

const add = (num1, num2) => num1 + num2;

const result = (num1, num2, cb) => {
  return "result is:" + cb(num1, num2);
}

const res = result(12, 13, add);