The cookie is a mechanism for storing persistent data on the client. Because HyperText Transport Protocol (HTTP) is a stateless protocol, cookies are used to provide a way to maintain information between client requests. You may store a maximum of 300 total cookies in the cookie file, at up to 4 Kbytes per cookie for the sum of both the cookie's name and value, and no more than 20 cookies per server or domain. Full documentation for cookies can be found in Netscape's JavaScript Guide.
- Standard Cookies
- Subdivided Cookies
- Try it
- Display Cookies and delete them
Standard Cookies:
The simplest cookie has a name to use for refering to it, a value that you may retrieve later, and an expiration date after which it will be erased. The subroutines to use for getting and setting such cookies are put into the <head> section of the page and may look like this:
<script type="text/javascript">
<!-- Hide this code from non-JavaScript browsers
function GetCookie(name) {
c1 = document.cookie;
c1 = c1.replace(/\n/g, ""); // drop nl chars
c1 = c1.replace(/\r/g, ""); // drop cr chars
ix1 = 0; // from beginning
c1 = c1 + ";"; // for final cookie
while (c1.indexOf(";", ix1) != -1) {
ix2 = c1.indexOf(";", ix1); // next cookie break
if (ix2 == -1) { ix2 = c1.length; }
c2 = c1.substring(ix1, ix2); // a single cookie
ix1 = ix2 + 1;
ix3 = c2.indexOf("=", 0); // name=value break
if (ix3 == -1) { ix3 = c2.length; }
c3 = c2.substring(0, ix3); // get the name
c4 = c2.substring(ix3 + 1); // get the value
c3 = c3.replace(/ /g, ""); // drop all spaces
if (c3 == name) { return unescape(c4); }
}
return true;
}
function SetCookie(name, value, expires, days) {
p3 = expires;
p4 = days;
if (!p3) { // no expiration
if (!p4) { p4 = 1; } // no days: use 1
p3 = new Date();
msd = 1000 * 60 * 60 * 24; // millisecs per day
p3.setTime(p3.getTime() + msd * days);
}
document.cookie=name+"="+escape(value)+"; expires="+p3.toGMTString();
return true;
}
// End hiding -->
</script>
The code to get and set cookies goes within the <body> at the point where you want them displayed. It might look like this:
<script type="text/javascript">
<!-- Hide this code from non-JavaScript browsers
lvdate = GetCookie("lvdate");
if (lvdate) {
xeq = "<p>";
xeq += "Your last visit was " + lvdate + ". ";
xeq += "It's nice to see you again.";
xeq += "</p>";
document.write(xeq);
}
lvdate = new Date();
SetCookie("lvdate", lvdate, "", 1);
// End hiding -->
</script>
Top / Standard Cookies / Subdivided Cookies / Try it / Display Cookies
Subivided Cookies:
It is possible to set a cookie's value to multiple name/value pairs to store multiple items per cookie. Subroutines to do this get a bit more complex than the standard ones listed above, and may look like this:
<script type="text/javascript">
<!-- Hide this code from non-JavaScript browsers
function GetCookie(name) {
var cookies = document.cookie; // cookies for site
var ix1; // loop index
var n1 = name; // main cookie name
var n2; // crumb name
var out; // returned value
ix1 = n1.indexOf(";"); // cookie/crumb break
if (ix1 != -1) {
n2 = n1.substring(ix1 + 1); // crumb name
n1 = n1.substring(0, ix1); // main cookie name
}
out = GetCookieCrumb(cookies, n1);
if (n2 && out) { out = GetCookieCrumb(out, n2); }
cookie = rest;
return out;
}
function SetCookie(name, value, expires, days) {
var cookies = document.cookie; // cookies for site
var ix1; // index
var n1 = name; // main cookie name
var n2 = ""; // crumb name
var out; // returned value
var p2 = value; // new value
var p3 = expires; // param work area
var p4 = days;
var msd = 1000 * 60 * 60 * 24; // millisecs per day
if (!p3) { // no expiration
if (!p4) { p4 = 1; } // no days: use 1
p3 = new Date();
p3.setTime(p3.getTime() + msd * days);
}
ix1 = n1.indexOf(";"); // cookie/crumb break
if (ix1 != -1) {
n2 = n1.substring(ix1 + 1); // crumb name
n1 = n1.substring(0, ix1); // main cookie name
}
out = GetCookieCrumb(cookies, n1);
if (n2) {
if (out) { out = GetCookieCrumb(out, n2); }
else { rest = ""; }
if (rest) { p2 = rest + ";" + n2 + "=" + p2; }
else { p2 = n2 + "=" + p2; }
}
document.cookie=n1+"="+escape(p2)+"; expires="+p3.toGMTString();
return true;
}
function GetCookieCrumb(instring, seeking) {
var c1; // cookies work area
var c2; // cookie work area
var c3; // cookie name
var c4; // cookie value
var ix1; var ix2; var ix3; var ix4; // indexes
var out; // return value
rest = "";
c1 = instring;
c1 = c1.replace(/\n/g, ""); // drop nl chars
c1 = c1.replace(/\r/g, ""); // drop cr chars
c1 = c1 + ";"; // for final cookie
ix1 = 0; // from beginning
if (seeking.substring(0, 1) == "#") {
if (seeking == "#0" && !instring) { return 0; }
ix4 = seeking.substring(1); // which item wanten
ix3 = 0; // none so far
while (c1.indexOf(";", ix1) != -1) {
ix2 = c1.indexOf(";", ix1);
cookie = c1.substring(ix1, ix2);
ix3 += 1;
if (ix3 == ix4) { return cookie; }
ix1 = ix2 + 1;
}
if (ix4 == 0) { return ix3; } // count of items
return "";
}
while (c1.indexOf(";", ix1) != -1) {
ix2 = c1.indexOf(";", ix1); // next cookie break
if (ix2 == -1) { ix2 = c1.length; }
cookie = c1.substring(ix1, ix2); // a single cookie
c2 = cookie; // cookie work area
ix1 = ix2 + 1;
ix3 = c2.indexOf("=", 0); // name=value break
if (ix3 == -1) { ix3 = c2.length; }
c3 = c2.substring(0, ix3); // get the name
c4 = c2.substring(ix3 + 1); // get the value
c3 = c3.replace(/ /g, ""); // drop all space
if (c3 == seeking) {
out = unescape(c4);
} else {
if (rest) { rest = rest + ";" + cookie; }
else { rest = cookie; }
}
}
return out;
}
// End hiding -->
</script>
To make use of a subdivided cookie, put a semicolon (;) after the main cookie name and then add the sub-name like this:
<script type="text/javascript">
<!-- Hide this code from non-JavaScript browsers
p_name = GetCookie("personal;name");
if (p_name) {
xeq = "<p>";
xeq += "I remember you, " + p_name + ". ";
p_adr = GetCookie("personal;address");
xeq += "You live at " + p_adr + ". ";
xeq += "</p>";
document.write(xeq);
}
SetCookie("personal;name", "Casey Jones", "", 10);
SetCookie("personal;address", "2 2 Twain St, Railway Station,Texas", "", 10);
// End hiding -->
</script>
Top / Standard Cookies / Subdivided Cookies / Try it / Display Cookies
Try it:
You may set up your favorite links to automatically appear on this page for the next three months:
Top / Standard Cookies / Subdivided Cookies / Try it / Display Cookies
Display Cookies:
If you are running a Windows 95/98 machine using Netscape in its
default configuration, your cookies are probably stored in
c:/Program%20Files/Netscape/Users/default/cookies.txt.
It may not be a display of all current cookies because
Netscape may still be holding some in memory. You would have
to shut down the browser and start it again to be certain of an
up-to-date file.
To get rid of Netscape cookies stored on your machine, select
"Edit > Preferences > Advanced," choose
"Disable cookies," select "OK," and then shut
down your browser. Do not attempt to edit the file directly.
On a Windows 95/98 machine set up for a single user, Internet
Explorer is probably storing its cookies in the
c:/Windows/Cookies/ directory.
If you wish to get rid of IE cookies, use Internet Explorer and
select "Tools > Internet Options > Settings > View
Files," look down the list under "Internet Address"
looking for anything that begins with "Cookie:," select
the entry, and then push the "delete" key. Repeat
the procedure for any other cookies on the list and then get back
out of the drop-down boxes.
.
