Question

I am looking for a way to create/detect a cookie on a local host in javascript. Basically, if a cookie with a specified name “foo” exists for the session, do nothing. If no cookie exists, then create a new cookie named foo and populate it with a guid. How can i do this in javascript?

Thanks

Answer 1

Reading cookies from javascript requires a bit of string parsing. There are a number of good libraries that make this task easier, but you can use code similar to the following to get and set cookie values

<script type="text/javascript">
    function GetCookieValue(key) {
        var value = null;
        var cookieArray = document.cookie.split(';');
        for (var i = 0; i < cookieArray.length; i++) {
            var keyValuePair = cookieArray[i].split("=");
            if (keyValuePair[0] == key) {
                value = keyValuePair[1];
                break;
            }
        }
        return value;
    }

    function SetCookieValue(key, value) {
        document.cookie = key + "=" + value;
    }
</script>

Generating a Guid in javascript is a bit harder. This guy has a nice library you can include that will generate good GUIDs. I know there are also some jQuery plugins that were created with a similar purpose, but I have not used them.

If you include the following scripts, along with the functions above it should do what you want.

<script type="text/javascript" src="http://www.broofa.com/Tools/Math.uuid.js"></script>
<script type="text/javascript">
    var guid = GetCookieValue("myGuid");
    if (guid == null)
        SetCookieValue("myGuid", Math.uuid());

    alert(GetCookieValue("myGuid"));
</script>