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Jaimal Dullat
Jaimal Dullat

Posted on • Originally published at Medium

Why Prototypal Inheritance is Key to JavaScript Development?

Ever browsed through JavaScript code and stumbled upon the words “prototype” or “prototypal inheritance”? If those terms sound more like a science experiment than a coding concept, you’re not alone. Today, we’re going to break down this seemingly complex topic into a simple and relatable explanation. So, buckle up, because we’re diving deep into the world of prototypes!

Setting the Stage: What’s Inheritance Anyway?

Imagine a family tree. You inherited your eyes from your mom and your wit from your dad. Similarly, in the programming world, one object can inherit properties and methods from another object. In JavaScript, this inheritance magic is performed by something called the prototype chain.

The Essence of Prototypal Inheritance

Objects in JavaScript have an internal property called [[Prototype]]. This isn't something you'll see in regular code, but it's always there behind the scenes. When you ask an object for a property (like myObject.myProperty), JavaScript will:

  • First, look for that property on myObject itself.

  • If it doesn’t find it, it will look on myObject's prototype.

  • If it’s not there, it continues up the chain until it finds the property or reaches an object with no prototype (end of the chain).

But Where Do These Prototypes Come From?

When you create a function, JS gives it a property called prototype. For example, if you create a function Dog(), you can attach properties and methods to Dog.prototype. When you create an object using new Dog(), the object's [[Prototype]] links to Dog.prototype.

 function Dog(name) { = name;

 Dog.prototype.bark = function() {
  console.log(`${} says woof!`);

 let buddy = new Dog('Buddy');
 buddy.bark(); // Buddy says woof!
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Here, buddy doesn’t have a bark method on itself. Instead, it uses the bark method on its prototype, Dog.prototype.

Can I Change The Prototype?

Absolutely! With the help of Object.create(), you can create a new object and set its prototype to an existing object.

 let mammal = {
  vertebrate: true,
  breathe: function() {
    console.log('Inhale... Exhale...');

 let human = Object.create(mammal);
 human.walk = function() {
  console.log('Walking on two legs!');

 human.breathe(); // Inhale... Exhale...
 human.walk();    // Walking on two legs!
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Though human doesn't have the breathe method, it accesses it through its prototype, mammal.

Why should I care about prototypal inheritance?

Here are some compelling reasons:

  1. Efficiency in Memory Usage:
    Unlike class-based languages where each instance of a class has its own set of methods, in JavaScript, shared methods are stored once on the prototype. This means that, regardless of the number of objects you create, the methods are not duplicated in memory. This leads to efficient memory usage, especially when you have numerous instances.

  2. Dynamic Object Behavior:
    One of the unique features of prototypal inheritance is the ability to modify an object’s behavior at runtime. By changing the prototype, all objects that inherit from that prototype will immediately get the updated behaviors without any additional work.

  3. Flexibility and Evolution:
    Prototypes allow for an evolutionary design approach. If you need to add new methods or properties, you can just append them to an object’s prototype, and all inheriting objects will immediately have access to these changes.

  4. Simplicity:
    In many ways, prototypal inheritance is simpler and more straightforward than class-based inheritance. You can create a new object that inherits from an existing one without the complexities of classes and constructors.

  5. Powerful Framework and Library Support:
    Many popular JavaScript frameworks and libraries, like Prototype and Node.js, make extensive use of prototypal inheritance. Understanding it will unlock a deeper comprehension of how these tools work and can be extended or modified.

  6. True to JavaScript’s Nature:
    JavaScript was designed to be a prototypal language. By using prototypal inheritance, you’re working with the grain of the language, leveraging its native strengths rather than trying to mimic other paradigms.

Beware of the Pitfalls

Prototypal inheritance is powerful, but it has its quirks. Overusing it can lead to confusing code. Also, modifying the prototype of built-in objects (like Array or Object) can introduce unexpected behaviors. It's crucial to use it judiciously.


JavaScript’s prototypal inheritance might seem intimidating at first, but it’s simply about objects borrowing properties and methods from other objects. Like a family tree, where traits are passed down, JavaScript objects pass down properties and methods through the prototype chain. Now that you’re equipped with this knowledge, go forth and code confidently!

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