Detailed explanation of JavaScript cookie and simple example application (picture and text tutorial)

This article mainly introduces the relevant information about the detailed explanation of JavaScript cookies and simple example applications. Here is a detailed explanation of the introduction, basic properties and simple applications of js cookies. Friends in need can refer to it

JavaScript cookie detailed explanation

1. Basic introduction to cookies

Cookie is the object of document. Cookies enable JavaScript code to store data persistently on the user's hard drive and to obtain data stored in this way. Cookies can also be used for client-side scripting.

Cookie data can be automatically transferred between Web browsers and Web servers.

In the browser, you can check whether the browser's cookie function is activated through the navigator.cookieEnabled attribute.

2. Basic attributes of cookie

Each cookie has four optional attributes

1.expires

Specifies the lifetime of the cookie. Set the expires attribute to an expiration time in the future to make the cookie invalid after expiration.

Now replace it with the max-age attribute, which sets the cookie's lifetime in seconds. Once the max-age lifetime is exceeded, the cookie will be automatically deleted from the cookie file by the browser

2.path

Specifies the cookie Web pages that are related together. By default, a cookie is associated with the web page that creates it, as well as web pages in the same directory as this web page and web pages in subdirectories of this directory.

This mainly sets the visibility of cookies to web pages. Add the path to www.a.com/list, then both www.a.com/list/a.html and www.a.com/list/b.html can access the cookie, but www.a.com/comtain This cookie cannot be accessed. But if the path is set to www.a.com/, then both www.a.com/list and www.a.com/contain can access the cookie.

3.domain

By default, only pages from the same web server can access cookies, and domain can be set. For example, if the cookie path is set to / and the cookie is set to .example.com, then all web pages located at catalog.example.com and orders.example.com, as well as web pages located on other servers under the .example.com domain name, can be accessed. This cookie

Note: You cannot set the domain of a cookie to a domain other than the domain where the server is located

4.source

source is a Boolean value, true is transmitted by insecure HTTP (default); false is only transmitted when the browser and server are connected through HTTPS or other secure protocols.

3. Application of cookies

A cookie is a string, composed of a name=value structure. Example of cookie:

version=1.0;max-age=3600

Note that commas or spaces cannot be included between each string, so in When writing a cookie, you need to use encodeURIComponent to remove the relevant symbols in the variable. When reading, use decodeURIComponent

To create a cookie that can last for one year:

document.cookie = “version=” + document.lastModified + “;max-age=” + (60*60*24*365);

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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