JavaScript objects and its internal representation

In real life object is an entity having state and behavior . For example: car, pen, bike, chair, glass, keyboard, monitor etc. In the same way JavaScript also has objects with properties as state and methods as behavior and they are represented in the form of

Creating Objects in JavaScript:

There are 3 ways to create objects.

1. By object literal
2. By creating instance of Object directly (using new keyword)
3. By using an object constructor (using new keyword)
4. By object literal:

The syntax of creating object using object literal is given below:

var object={property1:value1,property2:value2...,propertyN:valueN}

Here property and its value are separated by a colon (:) and the properties are separated by comma (,). The properties can be accessed using the dot (.) operator.

Example:

var car={name:"Renault",color:"red"};
console.log(car);//{ name: 'Renault', color: 'red' }
console.log("My car name is "+car.name);//My car name is Renault
console.log("My car color is "+car.color);//My car color is red

2. By creating instance of an object:

The syntax of creating object directly is given below:

var objectname=new Object();

Here, new keyword is used to create object.

Example:

var car=new Object();
car.name='Fiat';
car.color='red';
console.log(car);//{ name: 'Fiat', color: 'red' }

3. By using object constructor:

Here, we have to create function with arguments. Each argument value can be assigned in the current object by using this keyword which refers to the current object.

Example:

function car(name,color)
{
 this.name=name;
 this.color=color;
}
var car1=new car("Fiat","Red");
console.log(car1);//{ name: 'Fiat', color: 'red' }

Accessing object values:

We can access the object values by using dot (.) notation and bracket ([]) notation. If we are using bracket ([]) notation to access object values we have to specify the key as string within quotes (“”).

Example:

var car={name:"Renault",color:"red"};
console.log("Name :"+car.name);//Name :Renault
console.log("Name :"+car["name"]);//Name :Renault

Modifying object values:

We can use the dot (.) notation and bracket ([]) to modify any value in a JSON object.

Example:

var car1={name:"Renault",color:"red"};
var car2={name:"Fiat",color:"blue"};
car1.color="brownish red";
car2["color"]="metallic blue";
console.log(car1);//{ name: 'Renault', color: 'brownish red' }
console.log(car2);//{ name: 'Fiat', color: 'metallic blue' }

Deleting object properties:

Use the delete keyword to delete properties from a JSON object.

Example:

var car={name:"Fiat",color:"red",engine:"Chevy V8"};
delete car.engine;
console.log(car);//{ name: 'Fiat', color: 'red' }