Uncovering the hidden secrets of cookies: Uncovering this common but little-known way of storing data

Where cookies are hidden: Understanding this common but little-known way of storing data requires specific code examples

In our daily web browsing, we often I have heard about the concept of cookies, but most people’s understanding of cookies is limited to that it is a technology used to track user activities. However, it is less well known that cookies are actually a form of data storage that can be stored in different places on your computer, not just in your browser. In this article, we'll explore where cookies are hidden and provide specific code examples to better understand how cookies are stored.

1. Cookie storage on the browser side

The most common cookie storage location is the browser. When we visit a website, the website stores some information on our computer so that it can recognize us the next time we visit the website. This information is usually some basic user identification data, such as login status, shopping cart status, etc. The browser saves this information in a specific file, which is often called a cookie file.

In JavaScript, we can read and write cookie values ​​through document.cookie. The following is a simple sample code:

// 设置cookie
document.cookie = "username=John Doe; expires=Thu, 18 Dec 2023 12:00:00 UTC; path=/";

// 读取cookie
console.log(document.cookie);

In the above code, we set a cookie named "username" by assigning "username=John Doe" as the cookie value to document.cookie. This cookie will expire on December 18, 2023 and will be available throughout the entire website path. By printing document.cookie directly, we can see all cookie values ​​in the current page.

2. Server-side cookie storage

In addition to storing cookies in the browser, we can also store cookies on the server side. This is usually done to enhance cookie security and control. The most common way to store cookies on the server side is to use Sessions. Session is a server-side state management mechanism that implements user identity authentication and state maintenance by storing user information on the server.

The following is a simple sample code using Node.js and the Express framework:

// 通过设置session
app.get('/setSession', function (req, res) {
  if (!req.session.views) {
    req.session.views = 1;
  } else {
    req.session.views++;
  }
  res.send('Session value: ' + req.session.views);
});

// 通过获取session
app.get('/getSession', function (req, res) {
  res.send('Session value: ' + req.session.views);
});

In the above code, we use express-session middleware to implement the Session function. By accessing the "/setSession" interface, we can add a Session value named "views" and return the current Session value. By accessing the "/getSession" interface, we can obtain the current Session value.

3. Cookie storage in other hidden places

In addition to storing cookies in browsers and servers, we can also store cookies in other places, such as databases, file systems, memory, etc. This usually requires us to use specific technology and code to achieve this.

Taking storing cookies in the database as an example, the following is a simple sample code using PHP and MySQL:

// 连接数据库
$conn = new mysqli('localhost', 'username', 'password', 'database');

// 设置cookie
$cookie_value = time();
$sql = "INSERT INTO cookies (cookie_value) VALUES ('$cookie_value')";
$conn->query($sql);

// 读取cookie
$sql = "SELECT cookie_value FROM cookies";
$result = $conn->query($sql);
$row = $result->fetch_assoc();
echo "Cookie value: " . $row['cookie_value'];

In the above code, we set the cookie value by inserting it into the database cookies. And by querying the cookie value from the database, we can read it and display it on the page.

Summary:

Through the above code examples, we have an in-depth understanding of where cookies are hidden. In addition to common browser-side and server-side storage methods, we can also store cookies in databases, file systems, memory, etc. to meet different needs. No matter which storage method we choose, we should pay special attention to the security of cookies to avoid leakage of sensitive information. At the same time, reading and understanding how cookies are stored and code examples will help us better understand and apply cookie technology.

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