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How to use cookie in java script
Description A cookie is a variable that is stored on the visitor's computer.   No. of Views     1415
  Rating     4
Author Najmul Hoda   Posted On     01 Feb 2010
Tags Java Script    

Sample Code   Download Code

Introduction
Before explaining the article, I would like to thank all readers who read my article and voted for it. Your appreciation for my article gives me strength to write more good articles. Hope in future I will get your valuable comments and suggestions. Now I won't waste your time and come back to the topic. I have written this article on ‘What is a Cookie?’
A cookie is a variable that is stored on the visitor's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With JavaScript, you can both create and retrieve cookie values.
Examples of cookies:

Name cookie - The first time a visitor arrives to your web page, he or she must fill in her/his name. The name is then stored in a cookie. Next time the visitor arrives at your page, he or she could get a welcome message like "WelcomeNajmul!" The name is retrieved from the stored cookie
•    Password cookie - The first time a visitor arrives to your web page, he or she must fill in a password. The password is then stored in a cookie. Next time the visitor arrives at your page, the password is retrieved from the cookie

•    Date cookie - The first time a visitor arrives to your web page, the current date is stored in a cookie. Next time the visitor arrives at your page, he or she could get a message like "Your last visit was on Sunday August15, 2005!" The date is retrieved from the stored cookie.
Create and Store a Cookie
In this example we will create a cookie that stores the name of a visitor. The first time a visitor arrives to the web page, he or she will be asked to fill in her/his name. The name is then stored in a cookie. The next time the visitor arrives at the same page, he or she will get welcome message.
First, we create a function that stores the name of the visitor in a cookie variable:
function setCookie(c_name,value,expiredays)
{
var exdate=new Date();
exdate.setDate(exdate.getDate()+expiredays);
document.cookie=c_name+ "=" +escape(value)+
((expiredays==null) ? "" : ";expires="+exdate.toGMTString());
}
The parameters of the function above hold the name of the cookie, the value of the cookie, and the number of days until the cookie expires.
In the function above we first convert the number of days to a valid date, and then we add the number of days until the cookie should expire. After that we store the cookie name, cookie value and the expiration date in the document.cookie object. Then, we create another function that checks if the cookie has been set:
function getCookie(c_name)
{
if (document.cookie.length>0)
  {
  c_start=document.cookie.indexOf(c_name + "=");
  if (c_start!=-1)
    {
    c_start=c_start + c_name.length+1;
    c_end=document.cookie.indexOf(";",c_start);
    if (c_end==-1) c_end=document.cookie.length;
    return unescape(document.cookie.substring(c_start,c_end));
    }
  }
return "";
}
The function above first checks if a cookie is stored at all in the document.cookie object. If the document.cookie object holds some cookies, then check to see if our specific cookie is stored. If our cookie is found, then return the value, if not - return an empty string. Last, we create the function that displays a welcome message if the cookie is set, and if the cookie is not set it will display a prompt box, asking for the name of the user:
function checkCookie()
{
username=getCookie('username');
if (username!=null && username!="")
  {
  alert('Welcome again '+username+'!');
  }
else
  {
  username=prompt('Please enter your name:',"");
  if (username!=null && username!="")
    {
    setCookie('username',username,365);
    }
  }
}

About Author

About Author He is a team lead, having 8+ years of experience. He loves writing technical article for .Net developers. Najmul Hoda
No Photo
 
Country United States
Company BirlaSoft
Home Page http://www.magixchat.com

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Comments

 
 
Posted By Deepak Joshi on 04 Feb 2010 at 03:35 AM
 
Hi
such a nice work dear

really great
 
 
   
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