Class to interact with cookies

Question

Recently I needed to manipulate with cookies using JavaScript, so I wrote a class:

function Cookies() {
    var cookieLifeTime = null;

    this.setCookie = setCookie;
    this.getCookie = getCookie;
    this.deleteCookie = deleteCookie;
    this.setLifeTime = setLifeTime;

    function setLifeTime(lifeTime) {
        cookieLifeTime = lifeTime;
    }

    function setCookie(name, value) {
        if (this.lifeTime !== null) {
            var date = new Date();
            date.setTime((date.getTime() + cookieLifeTime));
            var expires = '; expires=' + date.toGMTString();
        } else {
            var expires = '';
        }

        document.cookie = name + '=' + value + expires + '; path=/';
    }

    function getCookie(name) {
        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(name) === 0)
                return c.substring(name.length, c.length); //Edited. Reduced not extra iterations
        }

        return null;
    }

    function deleteCookie(name) {
        setCookie(name, '', -1);
    }
}

I am not a JavaScript developer so maybe I've over-complicated things. Are there parts that can be optimized (I mean readability mostly)? I am also interested if there could be some edge-cases where this script will fail.

Answer 1

As Dvorak said in the comments, your code is fine as-is. Still, I have some suggestions:

1. I'd forego the *Cookie suffix on the function names. Seems too verbose, considering the constructor is called Cookies already. Only trick is that you can't have function called delete as that's a reserved word, but remove works fine too.

2. I think you have a bug: In deleteCookie you call your own setCookie with a negative lifetime - but setCookie doesn't take a lifetime argument, so the cookie won't be deleted as expected.
   I'd fix this by adding such a 3rd argument to setCookie but making it optional:

   function setCookie(name, value, lifetime) {
     var date, expires = '';
     // default to cookieLifeTime if no arg was passed
     if( typeof lifetime !== 'undefined' ) {
       lifetime = cookieLifeTime);
     }
     if( lifetime ) {
       date = new Date();
       date.setTime(date.getTime() + lifetime);
       expires = '; expires=' + date.toGMTString()
     }    
     document.cookie = name + '=' + value + expires + '; path=/';
   }
   

3. The getCookie can be made considerably shorter with a bit or regular expression magic.

   function getCookie(name) {
     var pattern = new RegExp(name + '=([^;]+)', ''),
         match = document.cookie.match(pattern);
     if(match) {
       return match[1];
     }
     return null;
   }
   

4. As RoToRa says in another answer, a simple object literal might be neater, if you're willing to either skip the cookieLifeTime instance variable, or make it completely global. Here's how I'd probably write it:

   // lowercase, as it's no longer a constructor
   window.cookies = {
     set: function (name, value, lifetime) {
       var date, expires = '';
       // for mysterious reasons `NaN` is a number in JS,
       // so check for NaN too
       if( typeof lifetime === 'number' && !isNaN(lifetime) ) {
         date = new Date();
         date.setTime(date.getTime() + lifetime);
         expires = '; expires=' + date.toGMTString()
       }    
       document.cookies = name + '=' + value + expires + '; path=/';
     },
   
     get: function (name) {
       var pattern = new RegExp(name + '=([^;]+)', ''),
           match = document.cookie.match(pattern);
       if(match) {
         return match[1];
       }
       return null;
     },
   
     remove: function(name) {
       window.cookies.setCookie(name, '', -1);
     }
   };
   

Answer 2

The only thing I'd suggest is that there is no real need for it being a class, since it's basically a singleton. So I'd use:

var Cookies = {
  // The same as your function
};