JavaScript Object

Objects are properties and methods and resemble to real life objects.properties specify the characteristics or attributes of an object,while methods identify the behavior of an object.for example car,pen,table

JavaScript is an object-based language. Everything is an object in JavaScript.
JavaScript is template based not class based. Here, we don't create class to get the object. But, we direct create objects.

Two type of Object

1)Custom Objects
2)Built-in Objects

1)Custom Object

Three Ways Creating Custom Objects in JavaScript

By object literal
By creating instance of Object directly (using new keyword)
By using an object constructor (using new keyword)

Example-By object literal

<html>
<body>
<script>
emp={id:102,name:"Riya",salary:40000}
document.write(emp.id+" "+emp.name+" "+emp.salary);
</script>
</body>
</html>

Example-By creating instance of Object

<html>
<body>
<script>
var emp=new Object();
emp.id=101;
emp.name="Ravi Malik";
emp.salary=50000;
document.write(emp.id+" "+emp.name+" "+emp.salary);
</script>
</body>
</html>

Example-By using an object constructor

<html>
<body>
<script>
function emp(id,name,salary)
{
this.id=id;
this.name=name;
this.salary=salary;
}
e=new emp(103,"Riya",30000);
document.write(e.id+" "+e.name+" "+e.salary);
</script>
</body>
</html>

2) Built-in Object

The built-in Objects are static objects which can be used to extend the functionality in the script...........for example

String Object
Math Object
Date Object
Window Object
History Object
Navigator Object
Document Object

<html>
<body>
<script>
var full_name=new String("aptech student");
document.write("no. of characrter:"+full_name.length+"<br>")
document.write("no. of characrter:"+full_name.charAt(2)+"<br>")
document.write("no. of characrter:"+full_name.split("",5)+"<br>")
document.write("no. of characrter:"+full_name.toUpperCase()+"<br>")
/*date object*/
var today=new Date()
document.write(today.getDate()+"<br>")
document.write(today.getMonth()+"<br>")
document.write(today.getFullYear()+"<br>")
</script>
</body>
</html>

document.getElementById

<html>
<head>
<script>
function getcube()
{
var number=document.getElementById("number").value;
//alert(number*number*number);
document.write(number*number*number);
}
</script>
</head>
<body>
<form>
Enter No:<input type="text" id="number" name="number"/><br>
<input type="button" value="cube" onclick="getcube()"/>
</form>
</body>
</html>

document.getElementByClass

<html>
<body>
<div class="example">
A div element with class="example"
</div>
<div class="example">
A div element with class="example"
</div>
<p class="example">
A p element with class="example"
</p>
<p>The number of elements with class="example" is:</p>
<p id="demo"></p>
<script>
var numb = document.getElementsByClassName("example").length;
document.getElementById("demo").innerHTML = numb;
</script>
</body>
</html>