Passing a function as a callback in JavaScript

Following is the code for passing a function as a callback in JavaScript −


 Live Demo

<!DOCTYPE html>
<html lang="en">
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   .result {
      font-size: 20px;
      font-weight: 500;
      color: blueviolet;
<h1>Passing a function as a callback</h1>
<div class="result"></div>
<button class="Btn">CLICK HERE</button>
<h3>Click on the above button to pass the add2() function as callback to multiply9() function</h3>
   let resEle = document.querySelector(".result");
   function add2(a) {
      return a + 2;
   function multiply9(fn, num) {
      return fn(num) * 9;
   document.querySelector(".Btn").addEventListener("click", () => {
      resEle.innerHTML = "The number returned = " + multiply9(add2, 12);


On clicking the ‘CLICK HERE’ button −

Updated on: 20-Jul-2020


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