Prevent data loss on webpage refresh by using Angular's local storage feature

Question

Prevent data loss on webpage refresh by using Angular's local storage feature

As a beginner in Angular, I am exploring ways to retain user input and interactions on my webpage even after a refresh. After some research, I came across using local storage as a viable solution. A different answer suggested utilizing the following code snippets for setting and getting information:

Storage.prototype.setObj = function(key, obj) {
    return this.setItem(key, JSON.stringify(obj))
}
Storage.prototype.getObj = function(key) {
    return JSON.parse(this.getItem(key))
}

But, I still have a couple of lingering questions:

I want the data to be saved upon refresh without continuous updates, so is there a way to handle this just before a refresh event? Or would it be necessary to constantly update local storage with every change?
When should I retrieve the data? Would placing the get function in my constructor make sense for this purpose?

javascript angular typescript angular-local-storage

Answer 1

Answer №1

Responding to your inquiries

To streamline auto-saving, simply save to localStorage whenever there is a change, but do so with a throttle (e.g. max once every second). There is an event that triggers when the tab is closed, onbeforeunload, although it may not fire if the tab crashes, and JavaScript's capabilities within this callback are limited.
When the page is reloaded, it is advisable to use the data from localStorage to establish the initial state, so load the data in one of the constructors

By the way, utilize localStorage.getItem() and localStorage.setItem(). You do not need to set prototypes.

Answer 2

Responding to your inquiries

To streamline auto-saving, simply save to localStorage whenever there is a change, but do so with a throttle (e.g. max once every second). There is an event that triggers when the tab is closed, onbeforeunload, although it may not fire if the tab crashes, and JavaScript's capabilities within this callback are limited.
When the page is reloaded, it is advisable to use the data from localStorage to establish the initial state, so load the data in one of the constructors

By the way, utilize localStorage.getItem() and localStorage.setItem(). You do not need to set prototypes.

Answer 3

Answer №2

It is not recommended to define any methods over a browser API prototype.
Due to the asynchronous nature of localStorage, it is important to inform Angular about these changes in order for the ChangeDetector to function properly.

To address these issues in my projects, I have created a service:

import {Observable} from 'rxjs';
import {Injectable, NgZone} from '@angular/core';

@Injectable()
export class StorageService {
  private localStorage: Storage = localStorage;

  constructor(
    private _zone: NgZone
  ) {
  }

  /**
   * Set a key in the browser's localStorage
   * @param key
   * @param data
   * @returns {Observable<any>}
   */
  public set(key, data): Observable<any> {
    return new Observable((observer) => {
      this.localStorage.setItem(key, JSON.stringify(data));
      this._zone.run(() => {
        observer.next(true);
        observer.complete();
      });
    });
  }

  /**
   * Retrieve a key from the browser's localStorage
   * @param key
   * @returns {Observable<any>}
   */
  public get(key): Observable<any> {
    return this._zone.run(() => {
      return new Observable((observer) => {
        setTimeout(() => {
          observer.next(
            JSON.parse(this.localStorage.getItem(key))
          );
          observer.complete();
        }, 0);
      });
    });
  }

  /**
   * Remove a key from the browser's localStorage
   * @param key
   * @returns {Observable<any>}
   */
  public remove(key): Observable<any> {
    return new Observable((observer) => {
      this.localStorage.removeItem(key);
      this._zone.run(() => {
        observer.next();
        observer.complete();
      });
    });
  }
}

Simply add this service to your module providers, inject it into your controller or service, and start using it.

Answer 4

It is not recommended to define any methods over a browser API prototype.
Due to the asynchronous nature of localStorage, it is important to inform Angular about these changes in order for the ChangeDetector to function properly.

To address these issues in my projects, I have created a service:

import {Observable} from 'rxjs';
import {Injectable, NgZone} from '@angular/core';

@Injectable()
export class StorageService {
  private localStorage: Storage = localStorage;

  constructor(
    private _zone: NgZone
  ) {
  }

  /**
   * Set a key in the browser's localStorage
   * @param key
   * @param data
   * @returns {Observable<any>}
   */
  public set(key, data): Observable<any> {
    return new Observable((observer) => {
      this.localStorage.setItem(key, JSON.stringify(data));
      this._zone.run(() => {
        observer.next(true);
        observer.complete();
      });
    });
  }

  /**
   * Retrieve a key from the browser's localStorage
   * @param key
   * @returns {Observable<any>}
   */
  public get(key): Observable<any> {
    return this._zone.run(() => {
      return new Observable((observer) => {
        setTimeout(() => {
          observer.next(
            JSON.parse(this.localStorage.getItem(key))
          );
          observer.complete();
        }, 0);
      });
    });
  }

  /**
   * Remove a key from the browser's localStorage
   * @param key
   * @returns {Observable<any>}
   */
  public remove(key): Observable<any> {
    return new Observable((observer) => {
      this.localStorage.removeItem(key);
      this._zone.run(() => {
        observer.next();
        observer.complete();
      });
    });
  }
}

Simply add this service to your module providers, inject it into your controller or service, and start using it.

Prevent data loss on webpage refresh by using Angular's local storage feature

Answer №1

Answer №2

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