How to handle cookies in JavaScript ?

I am working on a project where it requires to check cookie and tell whether it is 20 minutes old or not. So I have written once code which is like this. This is only javascript code I have pasted.

function checkcookie()
{
    var difftime= getcookie();
    // further operation comes here
}

var cookieminutes;

function getcookie()
{
    var start = document.cookie.indexOf("expires");
    var cookiedate;

    if(start==-1)
    {
        cookiedate = new Date();
        document.write("Start equal to -1");
        document.cookie="expires="+cookiedate+",path=0,domain=0";
        cookieminutes= cookiedate.getMinutes();
    }
    else
    {
        document.write("Start not equal to -1");

        var date =  new Date();
        var minutes = date.getMinutes();

        document.write("The difference is "+minutes);
        document.write("<br />Cookie minutes is "+cookieminutes);
        return (minutes-cookieminutes);

    }
}

In function getcookie the variable cookieminutes is coming as undefined. But as I know since it is a global variable it should have the value.

Can anybody please tell what is the solution for this.?

From stackoverflow

• If you want to use global variables (generally bad design) set and access them explicitly with window. E.g.:

  window.cookieminutes = cookiedate.getMinutes();
  

  and later:

  document.write("Cookie minutes is "+window.cookieminutes);
  

  And drop the var cookieminutes;

  As I said in my comment, it looks like if getcookie is being called for the first time on a given page load, and the cookie exists (start != -1), cookieminutes is never set. You need to make sure you don't use undefined variables.

  Steve Harrison : Can you provide a link that supports this point of view? I haven't come across this before.

  Matthew Flaschen : Which point of view are you referring to? Global variables are a well-known code smell.

  stefpet : I assume it is the point of view of using globals by explicitly setting/getting them using the window object (instead of not explicitly using window).

  Steve Harrison : Yes, I know that global variables should be avoided if possible. I'm curious about your statement "set and access them explicitly with window". I know that implied globals are bad, but why should you always use "window" when referring to or setting global variables in JavaScript?

  Matthew Flaschen : I never said you always had to. I just think it's better to be explicit in this case.

• Please refer to this similar SO post:
  what-is-the-best-way-to-get-and-set-a-single-cookie-value-using-javascript

• You're only setting a value for cookieminutes in the top section of the if statement, so any references in the else section will be null.

  Try this:

  function getcookie()
  {
      var start = document.cookie.indexOf("expires");
      var cookiedate;
  
      cookiedate = new Date();
      cookieminutes = cookiedate.getMinutes();
  
      if(start==-1)
      {    
          document.write("Start equal to -1");
          document.cookie="expires="+cookiedate+",path=0,domain=0";    
      }
      else
      {
          document.write("Start not equal to -1");
  
          var date =  new Date();
          var minutes = date.getMinutes();
  
          document.write("The difference is "+minutes);
          document.write("<br />Cookie minutes is "+cookieminutes);
          return (minutes-cookieminutes);
  
      }
  }
  

  Chaithra : Ur code is working... But if I use that cookieminutes and minutes both will be same value. I have to get a 20 mins differnece between the 2 because of my project requirement. so can u pls post some other solution thank u ..

  Matthew Flaschen : I don't understand the reference to 20 minutes. As jim0thy and I said, your original code was using cookieminutes before setting it. You need to initialize it properly, probably by reading the cookie. If you don't know how to read cookies see http://www.quirksmode.org/js/cookies.html

  jim0thy : Ok, after looking into this a bit, it would seem that the expiration date of a cookie is write-only, so JS can't read it. document.cookie.indexOf("expires") looks for a cookie NAMES "expires", and does not retrieve the expiration date. It looks like the only way around this is to create a 2nd cookie, and set it's value to the expiration date of the 1st cookie. Sorry.