JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

When you assign a new cookie value to document.cookie, the current cookies are not
replaced. The new cookie is parsed and its name/value pair is appended to the list. The
exception is when you assign a new cookie with the same name (and same domain and path, if
they exist) as a cookie that already exists. In this case, the old value is replaced with the new.
For example:
document.cookie = "username=fritz";
document.cookie = "username=thomas";
alert("Cookies: " + document.cookie);
The result is
Reading Cookies
As you can see from the previous example, reading cookies is as simple as examining the
document.cookie string. Because the browser automatically parses and adds any cookies set
into this property, it always contains up-to-date name/value pairs of cookies for the current
document. The only challenging part is parsing the string to extract the information in which you
are interested. Consider the following code:
document.cookie = "username=fritz";
document.cookie = "favoritecolor=green";
document.cookie = "jsprogrammer=
The value of document.cookie after these statements are executed is
"username=fritz; favoritecolor=green; jsprogrammer=
If you are interested in the favoritecolor cookie, you could manually extract everything after
favoritecolor= and before ; jsprogrammer=. However, it is almost always a good idea to write
a function that will do this for you automatically.
Parsing Cookies
The following code parses the current cookies and places them in an associative array indexed
by name. It assumes that the browser is ECMAScript-compliant (nearly all modern browsers
are).
// associative array indexed as cookies["name"] = "value"
var cookies = new Object();
function extractCookies()