JavaScript DOM-10 Cookies (cookie overview, cookie manipulation)

I. Overview of Cookies

Cookie Introduction

-Cookies are key/value pairs that are generated by the server and stored in the client file system (. txt format), which automatically sends the saved Cookie back to the server when the browser requests the page on that site again

-Cookies allow the browser to pass data between different requests that visit the same site, allowing the server program to identify different clients

-Typical application: Save the user login status, tracking user behavior, page customization, save the shopping cart, etc. need to save the global variables of the occasion

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Storage of cookies

-Cookies are stored in a. txt text file in a specific directory on the client, and cookie data from different sites are kept in different files

-Cookie data is usually saved after encryption

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Expiration and scope

-Validity period: A cookie can specify a expires value that defines its lifetime, during which the cookie is valid and the cookie is cleared. Some pages will have a cookie with a lifetime of "0" or a negative value, so that when the browser is closed, the cookie is cleared immediately, the user information is not recorded, and more secure

-Scope: By default, the cookie saved by a site can only be accessed by itself and cannot be used by other sites. However, you can set the domain and path values of the cookie, and define which paths under which domain can access the cookie

Second, Cookie operation

Save cookies

-Cookies can be created by server-side programs (Java, PHP, etc.) and sent to the client for saving, or can be created and saved by client JavaScript scripts

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Read cookies

-Allows Document.cookie to obtain all cookies that the current site can read (between multiple cookies; separate)

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The life cycle of a Cookie

-If the Expires attribute is not specified, the cookie created is actually saved in memory, and the browser is destroyed when it is closed.

-You can use expires to specify its life cycle when saving cookies

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Summary: This chapter covers JavaScript DOM cookies (Cookie overview, cookie manipulation)

This article from the "Flying Ants" blog, declined to reprint!

JavaScript DOM-10 Cookies (cookie overview, cookie manipulation)