43 Prototypes

Prototypes are the mechanism by which JavaScript objects inherit features from one another.

1. Get Started

• Write this object in chrome browser console and then type user.
• We will observe the name property comes and a bunch of other properties

const user = {
    name: 'Biswajit'
}

• Similarly for array const hobbies = ['read','eat','play']
• We can observe there are methods like length, push, pop when we do hobbies.
• For function also greet. we can observe call, bind, apply etc are popping up

function greet(){
    console.log('Hello');
}

• It happens to primitive data types also const username = 'Mark' and then do username.
• We haven't defined those so how those are getting added to our object/variable/function?
• It happens due to prototype

2. Prototypes

• In Javascript if we create an object or instance of a function
• A prototype object is automatically associated with that object or instance.
• This prototype object is used to look up properties and methods that are not directly present on the object itself.
• We can access the prototype object using __proto__ or Object.getPrototypeOf(myObj)

const user = {
    name: 'Biswajit'
}
user.__proto__
Object.getPrototypeOf(user)

3. Object Prototype

• When we create an object (e.g user), its proto property points to Object.prototype

user.__proto__ === Object.prototype   //returns true

• For arrays it points to Array.prototype

hobbies.__proto__ === Array.prototype    //returns true