Introduction
Objects are used to store collections of data and complex entities. Objects are variables too, but they can contain many values. JavaScript objects belong to the Non-Primitive Data type.
There are two types of Objects,
- User-defined Objects
- Built-in Objects
User-defined Objects
In the objects defined/created by the user to solve any given problem. Users can create objects, such as Student, House, Car, Company, etc.
Built-in Objects
A built-in object is an object that is of the primitive and non-primitive data types, handling some specific tasks. They are different types of Objects in JavaScript.
Common reference Objects
- Array Object
- Boolean Object
- Math Object
- Date Object
- String object
- Regular Expression Object
DOM (Data Object Model)
- Attributes Object
- Element Object
- Style Object
- Document Object
BOM (Browser Object Model)
- Windows Object
- Navigator Object
- Location Object
- Screen Object
- Storage Object
Object Creation
There are three types of objects that can be created in JavaScript.
- By Object literal
- By creating an instance of the object
- By using Constructors
We can access the properties and method of the object,
- By Dot operator – objname. property value
- By Square brackets – [property]
Creating an object in a literal way
Example
<!DOCTYPE html>
<html>
<head>
<title>Objects in JavaScript</title>
<meta charset="utf-8">
</head>
<body>
<h2>By Object literal</h2>
<script type="text/javascript">
var student={}; //literal
student.name= 'VijayKumar';
student.rollno= '17CS095';
student.dept= 'CSE';
student.year= '3rd year';
document.write(student.rollno);
</script>
</body>
</html>
Output
Creating Instance of an Object
Example
<!DOCTYPE html>
<html>
<head>
<title>Objects in JavaScript</title>
<meta charset="utf-8">
</head>
<body>
<h2>Instance Of an Object</h2>
<script type="text/javascript">
var Faculty= new Object(); // instance of an Object
Faculty.name= 'RajKumar';
Faculty.rollno= '950';
Faculty.dept= 'ECE';
Faculty.salary= '30,000';
document.write("Faculty name :"+Faculty.name,"<br/>"+"Depeartment :"+Faculty.dept);
</script>
</body>
</html>
Output
By using a Method Constructors
Example
<!DOCTYPE html>
<html>
<head>
<title>Objects in JavaScript</title>
<meta charset="utf-8">
</head>
<body>
<h2>Constructor Objects</h2>
<script type="text/javascript">
function student(name, rollno, dept, year,) //Methods constructor
{
this.name=name;
this.rollno=rollno;
this.dept=dept;
this.year=year;
}
var student1= new student("Vijay",95,"CSE","3rd year");
var student2= new student("Surya",80,"ECE","3rd year");
var student3= new student("Naveen",90,"EEE","2rd year");
document.write(student1.dept,"<br />");
document.write(student2.name);
</script>
</body>
</html> 
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