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In order to use cookies on a page you need:
- a function that reads the cookie (if present)
- a function that stores the cookie
- a function that deletes the cookie
Below are three functions that perform these tasks:
- getCookie
- setCookie
- delCookie
function getCookie(NameOfCookie)
{
// First we check to see if there is a cookie stored.
// Otherwise the length of document.cookie would be zero.
if (document.cookie.length > 0)
{
// Second we check to see if the cookie's name is stored in the
// "document.cookie" object for the page.
// Since more than one cookie can be set on a
// single page it is possible that our cookie
// is not present, even though the "document.cookie" object
// is not just an empty text.
// If our cookie name is not present the value -1 is stored
// in the variable called "begin".
begin = document.cookie.indexOf(NameOfCookie+"=");
if (begin != -1) // Note: != means "is not equal to"
{
// Our cookie was set.
// The value stored in the cookie is returned from the function.
begin += NameOfCookie.length+1;
end = document.cookie.indexOf(";", begin);
if (end == -1) end = document.cookie.length;
return unescape(document.cookie.substring(begin, end)); }
}
return null;
// Our cookie was not set.
// The value "null" is returned from the function.
}
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function setCookie(NameOfCookie, value, expiredays)
{
// Three variables are used to set the new cookie.
// The name of the cookie, the value to be stored,
// and finally the number of days until the cookie expires.
// The first lines in the function convert
// the number of days to a valid date.
var ExpireDate = new Date ();
ExpireDate.setTime(ExpireDate.getTime() + (expiredays * 24 * 3600 * 1000));
// The next line stores the cookie, simply by assigning
// the values to the "document.cookie" object.
// Note the date is converted to Greenwich Mean time using
// the "toGMTstring()" function.
document.cookie = NameOfCookie + "=" + escape(value) +
((expiredays == null) ? "" : "; expires=" + ExpireDate.toGMTString());
}
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function delCookie (NameOfCookie)
{
// The function simply checks to see if the cookie is set.
// If so, the expiration date is set to Jan. 1st 1970.
if (getCookie(NameOfCookie)) {
document.cookie = NameOfCookie + "=" +
"; expires=Thu, 01-Jan-70 00:00:01 GMT";
}
}
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MAKING IT WORK
Simply adding the above code to a page does not set any cookies. The functions are the tools you need in order to read, set, and delete cookies on your page.
The final step in adding a cookie to your page is to add a purpose to the cookie. Decide whether you want the cookie to store the user's name, the date of his last visit to your page or the preferred language. Or use the cookie for whatever purpose you wish.
In any case, the codes you need to add to the cookie scripts will be different.
RAW SCRIPT
Below is the cookie script without the comments. Copy and paste to use the script on your own site.
function getCookie(NameOfCookie)
{ if (document.cookie.length > 0)
{ begin = document.cookie.indexOf(NameOfCookie+"=");
if (begin != -1)
{ begin += NameOfCookie.length+1;
end = document.cookie.indexOf(";", begin);
if (end == -1) end = document.cookie.length;
return unescape(document.cookie.substring(begin, end)); }
}
return null;
}
function setCookie(NameOfCookie, value, expiredays)
{ var ExpireDate = new Date ();
ExpireDate.setTime(ExpireDate.getTime() + (expiredays * 24 * 3600 * 1000));
document.cookie = NameOfCookie + "=" + escape(value) +
((expiredays == null) ? "" : "; expires=" + ExpireDate.toGMTString());
}
function delCookie (NameOfCookie)
{ if (getCookie(NameOfCookie)) {
document.cookie = NameOfCookie + "=" +
"; expires=Thu, 01-Jan-70 00:00:01 GMT";
}
}
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"Better Than Books - As Easy As It Gets!"