How to clear cookies in native Node.js

When developing web applications using Node.js, cookies are the most common way to persist user information. However, sometimes we need to clear user's cookies in the application. In this article, we will introduce how to clear cookies natively in Node.js.

To clear cookies, you first need to understand how cookies are set. Generally speaking, we set the cookie to a list of attributes and then return it to the client as the response header. For example, the following is a code snippet that sets a cookie:

const http = require('http');

http.createServer((req, res) => {
  // 设置cookie
  res.setHeader('Set-Cookie', ['userId=12345']);
  // 发送响应
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(3000);

This code uses the res.setHeader method to set the cookie and sets the userId attribute to 12345 . In this case, every time the client requests this URL, an attribute named Cookie will be included in the request header with the value userId=12345.

To clear cookies, we need to set an attribute named Set-Cookie in the response header and set its value to userId plus a null character String, as shown below:

const http = require('http');

http.createServer((req, res) => {
  // 清除cookie
  res.setHeader('Set-Cookie', ['userId=; Max-Age=0']);
  // 发送响应
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(3000);

In this code, we set the Max-Age attribute to 0, telling the browser to delete the cookie immediately. When the request reaches the server, the server will receive an empty cookie and therefore can clear the user's saved information.

We can also use the expires attribute to set the validity period of the cookie to a time in the past so that the cookie can be cleared immediately. For example:

const http = require('http');

http.createServer((req, res) => {
  // 清除cookie
  res.setHeader('Set-Cookie', ['userId=; expires=Thu, 01 Jan 1970 00:00:00 GMT']);
  // 发送响应
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(3000);

This code sets the expiration date to January 1, 1970, which means the cookie has expired. When the request reaches the server, the server will receive an expired cookie so it can be deleted.

It should be noted that it is easy to set and clear cookies in native Node.js, but in actual applications, we usually use some Node.js frameworks and third-party packages to handle cookie-related operations. For example, the Express framework has a middleware called cookie-parser that can be used to parse and set cookies. This method will be easier to operate and the code will be more concise and clear.

In summary, the user's cookies can be cleared by setting the Max-Age and expires attributes. It's easy to clear cookies using native Node.js, but in practice, it's often better to use Node.js frameworks and third-party packages to handle cookie-related operations.

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