Tutorial :Can I modify or add cookies from JavaScript? [closed]


Exactly what are the restrictions for handling browser cookies from javascript? Can I check if cookies are enabled for example?


Yes! Read this excellent article about using cookies with JavaScript

Here's an excerpted code example.

function createCookie(name,value,days) {      if (days) {          var date = new Date();          date.setTime(date.getTime()+(days*24*60*60*1000));          var expires = "; expires="+date.toGMTString();      }      else var expires = "";      document.cookie = name+"="+value+expires+"; path=/";  }    function readCookie(name) {      var nameEQ = name + "=";      var ca = document.cookie.split(';');      for(var i=0;i < ca.length;i++) {          var c = ca[i];          while (c.charAt(0)==' ') c = c.substring(1,c.length);          if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);      }      return null;  }    function eraseCookie(name) {      createCookie(name,"",-1);  }  

And as for testing whether they are enabled. I like jldupont's answer.


You write a cookie and try to read back: this way, you'll know if cookies are enabled.


you can use navigator.cookieEnabled but I'm not sure if it's supported by all browsers.

For more information about cookies, check this


Can I check if cookies are enabled for example?

Yes, but not as easily as you think. navigator.cookieEnabled is a very general flag which does not cover exactly under what circumstances you may set a cookie.

For example, it's possible for session cookies to be allowed but persistent cookies blocked. So you're not really going to know whether a cookie-set will succeed unless you go ahead and try it, by setting a dummy document.cookie and then reading document.cookie back to see if it took.

In many browsers a persistent cookie will be downgraded to a session cookie when persistent cookies are disabled. But not IE, which will simply block it. You can try to detect that by setting both a persistent and a session cookie to document.cookie and seeing which if any survives.


There's a great article on quirksmode about cookie manipulation via JavaScript: http://www.quirksmode.org/js/cookies.html


The W3Schools JavaScript Cookies code has a bug in it. In the function setCookie this line:


JavaScript Date Object Properties:

getDate() - Returns the day of the month (from 1-31)    ...    getTime() - Returns the number of milliseconds since midnight Jan 1, 1970    ...     getDate() plus the number of days is not going to work.  I think it should be something like this:      expire = expiredays * 1000 * 60 * 60 * 24; // convert to milliseconds    var exdate = new Date( today.getTime() + (expire) );  

The cookie libraries at TechPatterns.com Javascript Cookie Script Get Cookie, Set Cookie, Delete Cookie Functions work better (#1 in Google results isn't always the best).

I tested code from both pages in IE8 and the first one caused my cookie to have an expire date of 1/1/2038 1:00 AM. The code from the second example set my cookie expire date to exactly 1 day from the time I tested it, just as expected.

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