Prototypal Inheritance

1. Built-in Constructor Functions

These are the built-in constructor functions provided by JavaScript.

function Array()
function Function()
function Promise()
function Object()
function String()
function Number(), etc.

2. Built-in Array Constructor Function

2.1 Default Properties and Methods

Properties:

constructor
length
prototype, etc.

Methods:

push()
pop()
splice()
shift(), etc.

2.2 Creating an Array with the new Operator (Older way of writing)

Syntax:

let myArray = new Array(item1, item2, ...);

let myArray = new Array("a", 2, true);
myArray.push("pen");

console.log(myArray);  // Array (4)["a", 2, true, "pen"]
console.log(myArray.length);  // 4

3. Prototype Property

The Prototype property will be shared across all the instances of their constructor function.

3.1 Accessing the Prototype of a Constructor Function

console.log(Array.prototype);

3.2 Accessing the shared Prototype of an Instance

let myArray = new Array("a", 2, true);
console.log(Object.getPrototypeOf(myArray));

3.3 Prototypal Inheritance

On calling the new() operator, all the properties and methods defined on the prototype will become accessible to the instance objects. This process is called Prototypal Inheritance.

4. Built-in Function Constructor Function

4.1 Default Properties and Methods

Properties:

name
length
constructor
prototype, etc.

Methods:

apply()
bind()
call()
toString(), etc.

4.2 Creating a Function with the new Operator (Older way of writing)

Syntax:

let myFunction = new Function("param1, param2, ...", function body);

let Car = new Function("color, brand",
  `this.color = color;
   this.brand = brand;
   this.start = function() {
     console.log("started");
  };`);

console.log(Function.prototype);

5. Instance Specific and Prototype Properties

5.1 Prototype Properties/ Methods

The Prototype Properties/ Methods are the properties or methods common across the instance objects.

Examples:

calculateAge
displayGreetings
displayProfileDetails
calculateIncome

5.1.1 Adding a Method to the prototype

function Person(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
}

Person.prototype.displayFullName = function() {
  return this.firstName + " " + this.lastName;
};

let person1 = new Person("Virat", "Kohli");
let person2 = new Person("Sachin", "Tendulkar");

console.log(Object.getPrototypeOf(person1) === Object.getPrototypeOf(person2));

5.2 Instance-Specific Properties/ Methods

The Instance Specific Properties/ Methods are the properties or methods specific to the instance object.