Functions

function is a set of executable statement function we are using for re usability .they are mainly divided into 2types
 1. Free defined function
2. user defined function
 Free Defined Function :-
             They are built in  function available in the language

example :-

      alert, prompt
  User Defined Functions :-
     if any function is defined by the programmer at a time of project development comes under user defined functions
<script  type ="text/java script" language="java script">
function fun1()
{
    var x=100;
   var y=200;
   var z=300;
   alert (Z)
} </script>
<input type ="button" value="click"onclick ="fun1()"> 


we can also pass some values into the function this concept is called as Function with arguments
<script type="text/javascript">
function fun1(x,y){
var z= x+y

alert(z);

}

    </script>

<input type="button" value="click" onclick="fun1(10,20)">


every function is return some value using the return key word this concept  called function with return type

example:-

<script type="text/javascript">
function fun1()
{
rval= fun2();
alert(rval);
}
function fun2()
{
z=200;
return z;
}
    </script>

<input type="button" value="click" onclick="fun1()">
variables :-
     a variable with the name of the memory location used  to store some values 
                     Types of Variables :-
                                                 Local Variables 
                                                Global  Variables 

local variables :-

                               a variable declarations with in the function is called  as local variable . we  can not access the localhost variable of function from another  functions
Note:-
 a function  contains any variables with out var comes under Global  variable 
   var Sno =1001;//global
 function  fun1()
{
var x=100//local variable
var y=200// local variable
z=300;//global variable
 fun 2()
}
function  fun2()
 {
alert(z);
 }
<</script>
<input type ="button" value="click" onkclick="fun1()>

Declaration location in java script:-

   java script we can declare different location  with in the header tag , body tag and we can  embed with html elements and url address bar   
window:-
java script window is an object providing number of properties and methods this properties we can call directory or we can call using window object

alert
by using this method we can display the message box in the web page 
prompet
     used to display the input dialog box

<script>
rval=window .prompt ("enter players name " );
alert ("rval ");
</script>
print:-
 display the print properties dialog box
<script>
print();
</script>

confirm():-

 it is display the conformation dialog box .it returns a Boolean values  true if we click on the ok button otherwise it return false 

<script>

rval =confirm ("you want to print");

if (rval)

{

print()

else

alert("can");

</script>.  

localtion:-     it this properties is use to open an external page in the current window 

<script>

function fun1()

{

window.location="abc.html";

 

}

</script>

window.open :-        open in external webpage in now window.

 

set interval:-this function is use to run a set of statement for every regular interval of time , contain the arguments name of the functions and interval in milliseconds 

clear interval :-

  by using this method  we can stop the functionality of set interval 
 <script>
x=set interval ("fun1()",2000)
function fun1()
{
alert("hi");
}
function funstop(){
clear interval(x);
}
</script>
 <input type="button" value="open" onclick="fun1()">
<input type="button" value="stop" onclick="funstop()">
set timeout;-  this  function call set of statements(anther function ) ofter certain time value  
<script>
set timeout("fun1()",6000);
function fun1()
{
alert("ok");
}
 
</script>
window.close():-
 to close the open window 
<script>
function fun1()
{
window .close();
}
</script>
<input type="button" value="click" onclick ="fun1()">. 

Date function in  java script  :-
in java script date is an object return the current date & time  information  of client system . it is providing number of methods  get (H,M,S)
get date 
get month 
get hours 
get minutes 
get seconds 
get year