Check if a cookie exists NOT using the jQuery cookie plugin

Question

I have a requirement, in jQuery, to show an alert if a cookie does not exist.

I cannot use the jQuery cookie plugin.

I've found a couple of scripts that I may be able to use, however, I cant seem to get them working in my jsfiddles. Can anyone assist me? Or are there other suggestions how to meet this requirement?

http://jsfiddle.net/JustJill54/a3tgP/2/

function getCookie(name) {
    var dc = document.cookie;
    var prefix = name + "=";
    var begin = dc.indexOf("; " + prefix);
    if (begin == -1) {
        begin = dc.indexOf(prefix);
        if (begin != 0) return null;
    }
    else
    {
        begin += 2;
        var end = document.cookie.indexOf(";", begin);
        if (end == -1) {
        end = dc.length;
        }
    }
    return unescape(dc.substring(begin + prefix.length, end));
}

$(document).ready(function(){ 
    var myCookie = getCookie("MyCookie");

    if (myCookie == null) {
        // do cookie doesn't exist stuff;
        alert("Cookie not found.");
    }
    else {
        // do cookie exists stuff
        alert("MyCookie");
    }
}

http://jsfiddle.net/JustJill54/hYvX3/1/

$(document).ready(function(){ 
var acookie = ReadCookie("cookiename");
if(acookie.length == 0)
 { 
    alert("Cookie not found."); 
 }
}

Is there something I am doing wrong that the fiddles above are not creating alerts like I'm expecting?

http://stackoverflow.com/questions/4003823/javascript-getcookie-functions/4004010#4004010 — SpYk3HH, Jun 07 '13 at 12:43
This is a really great guide to how cookies work, and he provides functions for reading and setting cookies (and his `readCookie` function returns 'null' if the cookie in question doesn't exist): http://www.quirksmode.org/js/cookies.html — Michael Schuller, Jun 07 '13 at 12:47
@MichaelCSchuller thanks, I'm pretty new to the cookies thing, so I will read up on the links that you and spYK3HH have shared. — jg100309, Jun 07 '13 at 13:04

adeneo · Accepted Answer · 2013-06-07T12:51:49.357

0

create a function that returns null or false if the cookie doesn't exist :

function getCookie(c_name) {
    var c_value = document.cookie,
        c_start = c_value.indexOf(" " + c_name + "=");
    if (c_start == -1) c_start = c_value.indexOf(c_name + "=");
    if (c_start == -1) {
        c_value = null;
    } else {
        c_start = c_value.indexOf("=", c_start) + 1;
        var c_end = c_value.indexOf(";", c_start);
        if (c_end == -1) {
            c_end = c_value.length;
        }
        c_value = unescape(c_value.substring(c_start, c_end));
    }
    return c_value;
}

var acookie = getCookie("cookiename");
if (!acookie) {
    alert("Cookie not found.");
}

FIDDLE

edited Jun 07 '13 at 12:51

answered Jun 07 '13 at 12:46

adeneo

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So I tried pasting what you sent into a fiddle, and running it, but nothing happens. Am I doing something incorrectly? [link] (http://jsfiddle.net/JustJill54/MwKpP/) – jg100309 Jun 07 '13 at 12:59
Yeah, you're not closing the document ready function, but you don't need that, as there is no DOM manipulation -> [fiddle](http://jsfiddle.net/MwKpP/2/) – adeneo Jun 07 '13 at 13:18
Thanks @adeneo! I will play around with this. BTW. I just saw the link on your first post to the fiddle. – jg100309 Jun 07 '13 at 13:37

score 0 · Answer 2 · answered Jun 07 '13 at 12:56

function getCookie(name) {  
    var a = name + "=";  
    var al = a.length;  
    var cl = document.cookie.length;  
    var i = 0;  
    while (i < cl) {    
        var j = i + al;    
        if (document.cookie.substring(i, j) == a)    
        {
            var endstr = document.cookie.indexOf (";", j);  
            if (endstr == -1)    
                endstr = document.cookie.length;  
            return unescape(document.cookie.substring(j, endstr));
        }       
        i = document.cookie.indexOf(" ", i) + 1;    
        if (i == 0) break;   
    }  
    return null;
}

Check if a cookie exists NOT using the jQuery cookie plugin

2 Answers2