javascript Function-MK Tutorial

JavaScript Functions

A function is an independent reusable block of code that performs certain operations on variables and expression to fullfill a task.

function is used for reusebility of code.

Declaring a function

Function function_name()
{
body of the function
}

A function is Declare using function keyword
The basic rules of naming a function are similar to naming a variable.
The body of function is written within {}

Example-

<html>
<body>
<script>
function add()
{
var i,j;
i=parseInt(prompt("Enter a no:"));
j=parseInt(prompt("Enter a no:"));
document.write("res=",i+j);
}
add();//--------------------------------------->Function calling
</script>
</body>
</html>

Nesting with in function

<html>
<body>
<script>
function add()
{
var i,j;
i=parseInt(prompt("Enter a no:"));
j=parseInt(prompt("Enter a no:"));
document.write("res=",i+j);
}
function sub()
{
add();
var i,j;
i=parseInt(prompt("Enter a no:"));
j=parseInt(prompt("Enter a no:"));
document.write("<br>res=",i-j);
}
sub();
</script>
</body>
</html>

function with parameter

A parameter is a value that is passed when declaring a function.

Declaring parameterized function

Function function_name(name)
{
body of the function
}
function_name(name);

<html>
<body>
<script>
function add(i,j)
{
var i,j;
document.write("res=",i+j);
}
i=parseInt(prompt("Enter a no:"));
j=parseInt(prompt("Enter a no:"));
add(i,j);
</script>
</body>
</html>

function with return value

<html>
<body>
<script>
function add(i,j)
{
var i,j;
return i+j;
}
i=parseInt(prompt("Enter a no:"));
j=parseInt(prompt("Enter a no:"));
document.write(add(i,j));
</script>
</body>
</html>