HTTP cookies are fundamental elements in the world of web programming. These small pieces of information allow websites to store data in the user's browser to improve the browsing experience and personalize content. In this article, we will delve into how HTTP cookies work and how to program them correctly.
What are HTTP cookies?
HTTP cookies are text files that are sent from a web server to the user's browser via the HTTP protocol. These files are stored on the user's device and contain information relevant to the website, such as user preferences, login data and other personalized details.
HTTP cookies are essential in web programming, allowing websites to remember user interaction, serve personalized content, and track sessions. Additionally, HTTP cookies are used to implement security measures such as access control and identity verification.
How do HTTP cookies work?
The way HTTP cookies work is relatively simple. When a user visits a website, the server sends an HTTP response containing a cookie. The user's browser stores that cookie and sends it back to the server on each subsequent request, thus allowing the user's session to be maintained and the experience personalized.
HTTP cookies are classified into two types: session cookies and persistent cookies. Session cookies are temporarily stored on the user's device and are deleted when the browser is closed. On the other hand, persistent cookies have a defined expiration date and remain on the user's device until they are deleted or expire.
HTTP cookie programming
Correctly programming HTTP cookies is essential to ensure their proper functioning and guarantee user privacy. Next, we'll show you how to do it:
1. Set a cookie
```javascript const cookieName = 'my_cookie'; const cookieValue = 'my_value'; document.cookie = `${cookieName}=${cookieValue}; path=/`; ```
In the example above, a cookie is created with the name "my_cookie" and the value "my_value". The cookie is set using the "cookie" property of the "document" object. Additionally, the path ("/") is set to make the cookie available throughout the website.
2. Get the value of a cookie
```javascript function getCookie(cookieName) { const cookies = document.cookie.split(';'); for (let i = 0; i < cookies.length; i++) { const cookie = cookies[i].trim(); if (cookie.startsWith(cookieName + '=')) { return cookie.substring(cookieName.length + 1); } } return null; } const cookieValue = getCookie('my_cookie'); ```
In the example above, a function "getCookie" is created that takes the name of the cookie as a parameter. This function splits the cookie string into an array and loops through each cookie to find the one that matches the desired name. If it finds the cookie, it returns its value; otherwise it returns null.
3. Delete a cookie
```javascript function deleteCookie(cookieName) { document.cookie = `${cookieName}=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/;`; } ```
In the example above, a function "deleteCookie" is created that takes the name of the cookie as a parameter. This feature sets a cookie with an expiration date in the past, causing the browser to automatically delete it.
Frequently asked questions
Is it possible to read cookies from other websites?
No, cookies have a same origin policy, which means that only cookies from the same domain can be read.
How can I set an expiration date for a cookie?
You can set an expiration date for a cookie using the "expires" property when creating it. For example: document.cookie = 'my_cookie=my_value; expires=Thu, 31 Dec 2022 23:59:59 UTC; path=/;'
What is the size limit of an HTTP cookie?
The size limit of an HTTP cookie varies by browser, generally between 4KB and 10KB.
Are HTTP cookies secure?
HTTP cookies can be secure if implemented correctly and additional security measures are used, such as encryption of sensitive data.
Do HTTP cookies affect website performance?
The impact on performance depends on the size and number of cookies used. In general, an excessive number of cookies can increase the loading time of the website.
In conclusion, HTTP cookies are essential in web programming to provide a personalized user experience and ensure security measures. It is important to understand how they work and learn to program them correctly to take advantage of their full potential. We hope this article has been useful to you!
English 
Spanish