Replace/Append Cookies in JavaScript

Replace/Append Cookies

When we assign a new cookie value to document.cookie, the current cookie is 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.

Reading Cookie

We can read cookies by a document.cookie. The problem occurs when we need the specific part of the cookie to perform some action.

Deleting Cookies

A cookie is deleted by setting a cookie with the same name (and domain and path, if they were set) with an expiration date in the past and if using max-age then must set a negative value.

Ex:

Updating Cookies

A cookie is possible to update by setting a new value to a cookie with the same name.

Cookies Security Issues

  • Can misuse Client Details
  • Can track User
  • Client Can Delete Cookies
  • Client can Manipulate Cookies

Cookies Limitation

  • Support HTML4 / HTML 5
  • Each cookie can contain 4kb Data
  • Cookies can be stored in Browser and server
  • It is sent with each request
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How many create cookies in JavaScript?

JavaScript Cookies

Cookies are exposed as the cookie property of the Document object. This property is both readable and writeable.

You can see Cookies in Google Chrome by following chrome://settings/content/cookies

Creating Cookies

When you assign a string to document.cookie, the browser parses it as a cookie and adds it to its list of cookies. There are several parts to each cookies, many of them optional.

Syntax: –

document.cookie = “name=value”;
document.cookie = “name=value; expires=date; domain=domain; path=path; secure”;
document.cookie = “name=value; max-age=inSecond; domain=domain; path=path; secure”;

Ex:-

Creating Cookies

Optional Cookies Attribute:-

max-age
expires
domain
path
secure

Whenever you omit the optional cookie fields, the browser fills them in automatically with reasonable defaults.

max-age

It is used to create persistent cookies. It is supported by all modern browsers except IE.

Type of cookies: –

  • Session Cookies – Cookies that are set without the expires/max-age field are called session cookies. It is destroyed when the user quits the browser.
  • Persistent Cookies – The browser keeps it up until their expiration date is reached.

Ex:-

expires

It is used to create persistent cookies.

Type of cookies: –

  • Session Cookies – Cookies that are set without the expires/max-age field are called session cookies. It is destroyed when the user quits the browser.
  • Persistent Cookies – The browser keeps it up until their expiration date is reached.

Ex:-

document.cookie = “username=devops; expires=Monday, 3-Sep-2018 09:00:00 UTC”;

domain

It specifies the domain for which the cookie is valid. If not specified, this defaults to the host portion of the current document location. If a domain is specified, subdomains are always included.

Ex: –

path

Path can be / (root) or /mydir (directory). If not specified, defaults to the current path of the current document location, as well as its descendants.

Ex: – document.cookie = “username=devops; path=/”;

Ex: – document.cookie = “username=devops; path=/home”;

secure

Cookie to only be transmitted over secure protocol as https. Before Chrome 52, this flag could appear with cookies from http domains.

Ex: – document.cookie = “username=devops; secure”;

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What are cookies in JavaScript?

Cookies

A cookie is a small piece of text data set by the Web server that resided on the client’s machine. Once it’s been set, the client automatically returns the cookie to the webserver with each request that it makes. This allows the server to place values it wishes to ‘remember’ in the cookie, and have access to them when creating a response.

How Cookie Works

How Cookie Works

How Cookie Works

How Dangerous Cookies are

Type of Cookies

  • Session Cookies – Cookies that are set without the expires field are called session cookies. It is destroyed when the user quits the browser.
  • Persistent Cookies – The browser keeps it up until their expiration date is reached.
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