Posted on Aug 18 In a Single Page Application (SPA), each element has its own existence and lifecycle, rather than being part of a global page state. Authentication and authorization can affect some or all elements on the screen.Other concerns include third-party adaptation and server-side rendering for obtaining access tokens.Begin with a simple authentication form that requires a username and password. The API accepts the credentials and returns an access Token and refresh token.When the login is successful, save the information in localStorage:Upon revisiting the site, user information should be populated from localStorage.To manage the authentication state, use RxJS BehaviorSubject and Observable:If the localStorage status indicates the user is logged in and the page is refreshed, the user should be redirected to the appropriate location.To log out, remove the state and localStorage data:To protect private routes and redirect unauthorized users, use an AuthGuard:In future iterations, the access token can be used for API calls, and handling a 401 error can be implemented.To automatically add the access token to API calls, use an HTTP interceptor. This will help manage authentication headers for all requests.Register the interceptor in the app.module.ts:To handle 401 errors, create another interceptor that detects the error and refreshes the access token if necessary.Register the error interceptor in the app.module.ts:To display user information, create a component that subscribes to the authService.stateItem$ Observable and updates the UI accordingly.Include this component wherever it is needed to display user information.To redirect users to the original URL they were attempting to access before being redirected to the login page, store the URL during the authentication process.Update the AuthGuard to save the attempted URL:Add methods to the AuthService to store and retrieve the redirect URL:Modify the login component to redirect the user to the stored URL upon successful login:This will ensure that users are taken back to the original URL they attempted to access after logging in.To integrate third-party authentication providers, such as Google or Facebook, follow these general steps:If your application uses server-side rendering, you'll need to handle the initial authentication state differently. In this case, the access token can be fetched during the SSR process:For better security, your application should implement token refresh logic. When the access token expires, the application should use the refresh token to request a new access token without requiring the user to log in again.To further enhance the authorization process, you can implement role-based access control using roles and permissions.By implementing these additional features, you can create a robust and secure authentication and authorization system for your Single Page Application.In conclusion, adding a login system to a website makes it safer and easier to use. We talked about many steps like logging in, saving information, and making sure only the right people can see certain things. We also discussed some cool extra features, like using other websites to log in or giving different people different permissions. Following these steps will help create a cool and safe website that everyone enjoys using. Keep learning and improving your website over time!Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well Confirm For further actions, you may consider blocking this person and/or reporting abuse Rashid Shamloo - Aug 9 ilinieja - Jul 11 Sergey Leschev - Aug 8 Sergey Leschev - Aug 6 Once suspended, brainiacneit will not be able to comment or publish posts until their suspension is removed. Once unsuspended, brainiacneit will be able to comment and publish posts again. Once unpublished, all posts by brainiacneit will become hidden and only accessible to themselves. If brainiacneit is not suspended, they can still re-publish their posts from their dashboard. Note: Once unpublished, this post will become invisible to the public and only accessible to Super. They can still re-publish the post if they are not suspended. Thanks for keeping DEV Community safe. Here is what you can do to flag brainiacneit: brainiacneit consistently posts content that violates DEV Community's code of conduct because it is harassing, offensive or spammy. Unflagging brainiacneit will restore default visibility to their posts. DEV Community — A constructive and inclusive social network for software developers. With you every step of your journey. Built on Forem — the open source software that powers DEV and other inclusive communities.Made with love and Ruby on Rails. DEV Community © 2016 - 2023. We're a place where coders share, stay up-to-date and grow their careers.