How to Add a Method to a Prototype in JavaScript

This post covers how to add a method to a JavaScript prototype. Adding a method to the prototype is a great way to add functionality to all instances of a constructor.

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One of the advantages of working with JavaScript prototypes is that they allow you to add methods to objects at runtime. This can be extremely useful when you need to extend the functionality of existing objects, or when you want to share methods between multiple objects.

In this article, we’ll show you how to add a method to a prototype in JavaScript. We’ll also explain how this differs from adding a method directly to an object, and we’ll show you some uses for prototype methods.

What is a Prototype?

JavaScript objects have a property called a prototype. The prototype is an object that contains properties and methods that can be inherited by other objects. When you create an object, JavaScript automatically sets up its prototype. You can add new properties and methods to the prototype at any time.

What is Inheritance?

Inheritance is when an object or class is based on another object or class, using the same implementation. In JavaScript, inheritance is implemented via the prototype chain. All objects in JavaScript have a prototype, which is a reference to another object. When you try to access a property of an object, the runtime first looks for that property on the object itself. If it doesn’t find it, it looks for it on the prototype of the object, and so on until it either finds the property or reaches the top of the prototype chain (which is null).

Why Add Methods to a Prototype?

In JavaScript, adding a method to an object prototype is a shorthand way of making that method available to all objects of that type. It’s much like adding a method to a class in other programming languages.

There are several reasons you might want to add methods to a prototype:
-To keep your code DRY (Don’t Repeat Yourself). If you have several objects of the same type, adding methods to the prototype means you don’t have to add those methods to each individual object.
-To make your code more efficient. Once a method is added to the prototype, it is available to all objects of that type, so it doesn’t need to be recreated each time.
-To make your code more flexible and extensible. By adding methods to the prototype, you make them available for use by any code that references the object, not just the code that creates it. This can be useful if you need to allow someone else access to your objects or if you need to use third-party libraries with your objects.

How to Add a Method to a Prototype?

In order to add a method to a prototype, you must first select the prototype you wish to add the method to. This can be done by using the keyword “prototype” followed by the name of the object. For example, if you wanted to add a method to the “Person” prototype, you would use:

Person.prototype.methodName = function() {
// some code goes here

Where “methodName” is replaced with the name of the method you are adding.

What Happens When You Add a Method to a Prototype?

In JavaScript, when you add a method to a prototype, the method is added to all instances of the object. The reason for this is that when you create an object, the prototype of the object becomes the prototype of the instance. So, when you add a method to a prototype, it’s like adding a method to all objects that inherit from that prototype.

Where Can I Find More Information?

If you’re looking for more information on how to add a method to a prototype in JavaScript, there are plenty of resources available online. You can start by doing a search for “JavaScript prototype methods” or “JavaScript add method to prototype.”

Another great resource is the Mozilla Developer Network, which has an article on [Adding methods to prototypes](


In JavaScript, a prototype is an object that provides methods and properties for other objects.When you create a new object, you can specify its prototype as an existing object. All objects created from the new object will then inherit the methods and properties of the prototype object.

You can add methods and properties to a prototype at any time. For example, you might want to add a method to the Array prototype that formats an array as a comma-separated list. To do this, you would use the following code:

Array.prototype.toList = function() {
return this.join(“,”);

The toList method can now be used on any array:

var myArray = [1, 2, 3];
console.log(myArray.toList()); // outputs “1,2,3”

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