如何在Angular2中查看localStorage的更改？

Question

我试图找出如何让菜单显示和消失基于在以前的帖子中登录.但我认为一个更好也可能更容易的问题是,如何观察本地存储的变化？

我在本地存储中使用json web令牌进行身份验证,我很乐意看到对localStorage的更改,然后重新更新我对新信息的看法.

我用这个设置了localStorage

localStorage.setItem('jwt', my_token);

我想做的事情是检查我是否有令牌,如果我什么都没有发生,但是当发生变化时会发生事件.如果我只能观察像localStorage.getItem('jwt')这样的命名事件,我会特别喜欢它.

谢谢!

编辑:

Gunter指出了我正确的方向,但万一有人仍然相当困惑,这里有一个吸引人向你展示如何做到这一点. http://plnkr.co/edit/TiUasGdutCsll1nI6USC?p=preview

Answer 1

关键是要使用window.addEventListener("storage",.虽然图书馆可能是角度的"正确"方式,但这是我放在一起的"轻"版本,使用.bind(this)而不是在角度内部进行捣乱.

import { Injectable, OnDestroy } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Subject } from 'rxjs/Subject';
import 'rxjs/add/operator/share'

@Injectable()
export class StorageService implements OnDestroy {
  private onSubject = new Subject<{ key: string, value: any }>();
  public changes = this.onSubject.asObservable().share();

  constructor() {
    this.start();
  }

  ngOnDestroy() {
    this.stop();
  }

  public getStorage() {
    let s = [];
    for (let i = 0; i < localStorage.length; i++) {
      s.push({
        key: localStorage.key(i),
        value: JSON.parse(localStorage.getItem(localStorage.key(i)))
      });
    }
    return s;
  }

  public store(key: string, data: any): void {
    localStorage.setItem(key, JSON.stringify(data));
    // the local application doesn't seem to catch changes to localStorage...
    this.onSubject.next({ key: key, value: data})
  }

  public clear(key) {
    localStorage.removeItem(key);
    // the local application doesn't seem to catch changes to localStorage...
    this.onSubject.next({ key: key, value: null });
  }


  private start(): void {
    window.addEventListener("storage", this.storageEventListener.bind(this));
  }

  private storageEventListener(event: StorageEvent) {
    if (event.storageArea == localStorage) {
      let v;
      try { v = JSON.parse(event.newValue); }
      catch (e) { v = event.newValue; }
      this.onSubject.next({ key: event.key, value: v });
    }
  }

  private stop(): void {
    window.removeEventListener("storage", this.storageEventListener.bind(this));
    this.onSubject.complete();
  }
}

Answer 2

使用服务,只能从任何地方通过此服务访问LocalStorage.
然后,该服务可以提供在更改时发出事件的可观察对象,您可以订阅这些可观察对象以获得通知.

Answer 3

使用新的 rxjs 6更新了/sf/answers/3337816401/ 的版本。

import { Injectable, OnDestroy } from '@angular/core';
import { Subject } from "rxjs";
import { share } from 'rxjs/operators';

@Injectable()
export class StorageService implements OnDestroy {
    private onSubject = new Subject<{ key: string, value: any }>();
    public changes = this.onSubject.asObservable().pipe(share());

    constructor() {
        this.start();
    }

    ngOnDestroy() {
        this.stop();
    }

    public getStorage() {
        let s = [];
        for (let i = 0; i < localStorage.length; i++) {
            s.push({
                key: localStorage.key(i),
                value: JSON.parse(localStorage.getItem(localStorage.key(i)))
            });
        }
        return s;
    }

    public store(key: string, data: any): void {
        localStorage.setItem(key, JSON.stringify(data));
        // the local application doesn't seem to catch changes to localStorage...
        this.onSubject.next({key: key, value: data})
    }

    public clear(key) {
        localStorage.removeItem(key);
        // the local application doesn't seem to catch changes to localStorage...
        this.onSubject.next({key: key, value: null});
    }


    private start(): void {
        window.addEventListener("storage", this.storageEventListener.bind(this));
    }

    private storageEventListener(event: StorageEvent) {
        if (event.storageArea == localStorage) {
            let v;
            try {
                v = JSON.parse(event.newValue);
            } catch (e) {
                v = event.newValue;
            }
            this.onSubject.next({key: event.key, value: v});
        }
    }

    private stop(): void {
        window.removeEventListener("storage", this.storageEventListener.bind(this));
        this.onSubject.complete();
    }
}