javascript

Chapter 19: Client - Side Storage
string of all cookies available to the page (based on the domain, path, expiration, and security settings of
the cookies) as a series of name - value pairs separated by semicolons, as in the following example:
name1=value1;name2=value2;name3=value3
All of the names and values are URL - encoded and so must be decoded via decodeURIComponent() .
When used to set a value, the document.cookie property can be set to a new cookie string. That cookie
string is interpreted and added to the existing set of cookies. Setting document.cookie does not
overwrite any cookies unless the name of the cookie being set is already in use. The format to set a
cookie is as follows, which is the same format used by the Set - Cookie header:
name=value; expires=expiration_time; path=domain_path; domain=domain_name; secure
Of these parameters, only the cookie ’ s name and value are required. Here’s a simple example:
document.cookie = “name=Nicholas”;
This code creates a session cookie called “ name ” that has a value of “ Nicholas ” . This cookie will be sent
every time the client makes a request to the server; it will be deleted when the browser is closed. Although
this will work, there are no characters that need to be encoded in either the name or value, so it ’ s best to
always use encodeURIComponent() as shown in the following example when setting a cookie:
document.cookie = encodeURIComponent(“name”) + “=” +
encodeURIComponent(“Nicholas”);
To specify additional information about the created cookie, just append it to the string in the same
format as the Set - Cookie header, like this:
document.cookie = encodeURIComponent(“name”) + “=” +
encodeURIComponent(“Nicholas”) + “; domain=.wrox.com; path=/”;
Since the reading and writing of cookies in JavaScript isn ’ t very straightforward, functions are often used
to simplify cookie functionality. There are three basic cookie operations: reading, writing, and deleting.
These are all represented in the CookieUtil object as follows:
var CookieUtil = {
get: function (name){
var cookieName = encodeURIComponent(name) + “=”,
cookieStart = document.cookie.indexOf(cookieName),
cookieValue = null;
if (cookieStart > -1){
var cookieEnd = document.cookie.indexOf(“;”, cookieStart)
if (cookieEnd == -1){
cookieEnd = document.cookie.length;
}
cookieValue = decodeURIComponent(document.cookie.substring(cookieStart
+ cookieName.length, cookieEnd));
}
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