how to call a callback function code example

Example 1: call back function in javascript

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

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

processUserInput(greeting);

Example 2: 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 3: what are callbacks

/*
tl;dr: Callbacks are a way to force one function to complete,
before running another. Used for asynchronus programming.
*/

// Consider this example:
  
names = ['Anthony', 'Betty', 'Camie']

function addName(name, callback){
	setTimeout(function(){
    	names.append(name)
      	callback()
    }, 200)
}

function getNames(){
	setTimeout(function(){
    	console.log(names)
    }, 100)
}

addName('Daniel', getNames)
/* 
addName('Daniel', getNames) is saying:
'finish the function addName() BEFORE running the function getNames()'

> 'getNames()' here is the callback

Without the call back in this example, getNames would finish 
before addName. (setTimeout is used to force one function to go slower)

Callbacks are given as arguments to other functions

*/

Example 4: 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);