JavaScript Object With Example

Objects in JavaScript

JavaScript is an Object Oriented Programming (OOP) language. A programming language is called object-oriented if it has the following four basic capabilities: encapsulation, aggregation, inheritance and polymorphism. All The objects will have properties and methods.

Object Properties

  • Object properties can be any of the promitive data types or abstract data types.
  • Object properties are usually variables that are used internally in the object's methods, but can also be globally visible variables that can be used throughout the page.

  • Syntax for adding a property to an object

      objectName.objectProperty = propertyValue;


       var str = document.title;

    Object Methods

  • The methods are functions that let the object do something or let something be done to it.
  • A function is a standalone unit of statements and a method is attached to an object and can be referenced by the keywords.
  • Methods are useful for everything from displaying the contents of the object to the screen to performing complex mathematical operations on a group of local properties and parameters.
  • Example:

       document.write("This is a method of the object document");

    User-Defined Objects

    Apart from built-in objects, the users can also create their own objects. All user-defined objects and built-in objects are descendants of an object called Object. The new operator is used to create a new object.

    The new Operator

    The new operator is used to create an instance of an object. To create an object, the new operator is followed by the constructor method.


    var books = new Array("Sweta","Kavya");	

    in the above example Array() is a built-in object. Books is the instance of the objectArray().

    The Object() Constructor

    A constructor is a function that creates and initializes an object. The Object() constructor is used to build an object. The return value of the Object() constructor is assigned to a variable.

    The variable contains a reference to the new object. The properties assigned to the object are not variables. These properties can be accessed only through objects.

    Syntax to access the properties:

    Example: Creating an object

  • JavaScript numberr Object
  • Result:

       Book name is : Coding for world
       Book author is : aimtocode

    Defining methods for an Object

    Methods can be created using the objects.

    Example: Adding a function along with an object


       Book title is : Coding for world
       Book author is : Pvpn
       Book price is : 400

    In the above example, two methods are used. Book() is a constructor. So it does not need any object to access it.

    addPrice() is a user defined method. It has to be accessed through an object.

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