In web development, it is common to use cookie-based authentication to manage user sessions. This approach involves storing a unique token (known as a session cookie) on the client’s browser after successful user login. The session cookie is then sent with subsequent API calls to authenticate the user and grant access to protected resources.

In this article, we will explore how to implement cookie-based user authentication in JavaScript API calls. We will assume you already have a backend API that handles user authentication and issues session cookies upon successful login.

Sending Cookies with API Calls

JavaScript provides the fetch() function, which allows you to send HTTP requests to the server and retrieve data. By default, this function doesn’t include cookies when sending requests. However, you can enable cookie sending by adding the credentials: 'include' option.

Here’s an example of making an API call with cookies using the fetch() function:

fetch('https://api.example.com/data', {
  method: 'GET',
  credentials: 'include'
})
  .then(response => response.json())
  .then(data => {
    // Handle the response data
  })
  .catch(error => {
    // Handle any errors
  });

In this code snippet, https://api.example.com/data is the API endpoint you want to access. By including the credentials: 'include' option, the session cookie is sent along with the request.

Handling Authentication Errors

Sometimes, the session cookie may expire or become invalid due to various reasons (e.g., server-side session timeout or user logout). In such cases, the API might return an authentication error.

To handle authentication errors, you can check the response status code in the fetch() callback. For example, if the response status code is 401 Unauthorized, you can redirect the user to the login page to reauthenticate.

fetch('https://api.example.com/data', {
  method: 'GET',
  credentials: 'include'
})
  .then(response => {
    if (response.status === 200) {
      return response.json();
    } else if (response.status === 401) {
      // Redirect to login page
      window.location.href = '/login';
    } else {
      throw new Error('API request failed');
    }
  })
  .then(data => {
    // Handle the response data
  })
  .catch(error => {
    // Handle any errors
  });

In the code above, we check for a 401 Unauthorized status code and redirect the user to the login page if the API call is unauthorized.

Conclusion

By including the credentials: 'include' option in your API calls, you can easily implement cookie-based user authentication in JavaScript. This approach allows you to authenticate users and grant access to protected resources using session cookies.

Make sure to handle authentication errors gracefully to provide a seamless user experience.