Passing a function as a callback in JavaScript

Javascript Web Development Object Oriented Programming

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

Example

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   .result {
      font-size: 20px;
      font-weight: 500;
      color: blueviolet;
   }
</style>
</head>
<body>
<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>
<script>
   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);
   });
</script>
</body>
</html>