How to add a property, method to a JavaScript constructor?

JavascriptWeb DevelopmentObject Oriented Programming

Following is the code to add a property, method to a JavaScript constructor −


 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;
<h1>Add property,method to javaScript constructor</h1>
<div style="color: green;" class="result"></div>
<button class="Btn">CLICK HERE</button>
<h3>Click on the above button to add property, method to constructor</h3>
   let resEle = document.querySelector(".result");
   function Human(firstName,lastName){
      this.firstName = firstName;
      this.lastName = lastName;
   let obj = new Human('Rohan','Sharma');
   document.querySelector(".Btn").addEventListener("click", () => {
      Human.prototype.welcome = function(){
         return 'Welcome '+this.firstName + ' ' + this.lastName;
      Human.prototype.age = 22;
      resEle.innerHTML = 'Adding property to constructor : age <br>' + obj.age + '<br>';
      resEle.innerHTML += 'Adding function to constructor : welcome() <br>' +
      obj.welcome() + '<br>';


The above code will produce the following output −

On clicking the ‘CLICK HERE’ button −

Published on 16-Jul-2020 07:04:14