How to retrieve a cookie's value?

Question

I may be asking the wrong question but I am still fairly new to JavaScript. I need to create a cookie that will re-strict the number of usages a user has for an online product demo. In pseudo code, I assume it would be something like this:

if(readCookie('demo') == null){ 
 createCookie('demo','1',1);}  //Assuming the functions for setting a cookie and retrieving it have already been created.
else {
    readCookie('demo');
}

if demo cookie has value{
    increment the value by one
}
else if value exceeds 10 {
    alert message //I set this so I could test out the function
}

Any help would be appreciated!

Answer 1

This page will tell you everything you need to know and even provides example functions for you to plug into your own code to make cookie handling very easy.

http://www.quirksmode.org/js/cookies.html

Answer 2

If your open to using jQuery, you should look at the jquery.cookie plugin.

Examples (via Documentation):

Create session cookie:

$.cookie('the_cookie', 'the_value');

Create expiring cookie, 7 days from then:

$.cookie('the_cookie', 'the_value', { expires: 7 });

Create expiring cookie, valid across entire page:

$.cookie('the_cookie', 'the_value', { expires: 7, path: '/' });

Read cookie:

$.cookie('the_cookie'); // => 'the_value'
$.cookie('not_existing'); // => null

Delete cookie by passing null as value:

$.cookie

Answer 3

As noted by a user-comment, a cookie is not a good way to do this. You cannot enforce it.

That said, I wrote and maintain a JavaScript cookie API. Check it out at: http://code.google.com/p/cookies/ (It does NOT require jQuery, although it has extras built in if jQ is present).

Here is your pseudo code translated to use the lib: http://jsfiddle.net/JAAulde/BGFQs/ (You'll see the alert after clicking "Run" enough times)