Скачать или смотреть How to Keep BehaviorSubject Data Persistent Across Page Reloads in Angular 8

Learn how to retain user data in your Angular 8 app even after page reloads. This guide explains how to leverage `localStorage` for persistent storage of user information.
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This video is based on the question https://stackoverflow.com/q/63251219/ asked by the user 'Anas Masti' ( https://stackoverflow.com/u/11148546/ ) and on the answer https://stackoverflow.com/a/63251438/ provided by the user 'Neeraj Shende' ( https://stackoverflow.com/u/7792527/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Keep BehaviorSubject Data Persistent Across Page Reloads in Angular 8

As developers, we often encounter scenarios where we need to maintain the state of an application even after a user reloads the page. One common issue arises when we utilize BehaviorSubject in Angular for managing user authentication. Particularly, developers may find themselves unable to retrieve the current user's data after a page refresh. This guide aims to clarify why this happens and how to implement a solution effectively.

The Problem

Consider a situation where you're using an authentication service in Angular 8 to manage user sessions. After initial login, you may successfully retrieve and display the current user's information. However, upon refreshing the page, your application tends to lose this state, resulting in null values where user data should be displayed. For instance:

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This happens because the data stored in the BehaviorSubject does not persist through page reloads as it is in memory. Upon a refresh, the application is reinitialized, which means the BehaviorSubject is reset.

The Solution

To maintain user data across page reloads, we must persist it in a place the application can access after a refresh. A convenient approach is to leverage the localStorage or sessionStorage of the browser. Here's how to implement this in your Angular application:

Step 1: Store User Information in localStorage

When a user logs in, you can store their information in localStorage. This is done in the login method of your AuthService. You are already using localStorage to save the access_token, so you should also store the user details when you retrieve them:

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Step 2: Retrieve User Information on Component Initialization

In your component class (e.g., PageComponent), retrieve the user information from localStorage within the ngOnInit() method to ensure your application reads the user's data even after a refresh:

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Summary

To ensure that your application's user information remains available after a page reload:

Store the user data in localStorage when the user logs in.

Retrieve the data from localStorage when initializing your component.

By following these steps, you'll be able to enhance the user experience of your Angular application without the frustration of losing session state due to page reloads.

Final Thoughts

Handling user state management in Angular can be tricky, but by using localStorage, you can effectively bridge the gap caused by page refreshes. Implement these strategies into your application, and ensure a seamless user experience every time.

Happy coding!