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Every time one or several values are changed (added, removed or updated) through the LocalStorage or SessionStorage class, a StorageEvent of type change is emitted

These events are exposed as an Observable, you can subscribe to it using the onChange property:

import {Component, OnInit, SimpleChanges} from "@angular/core";
import {LocalStorage} from "@cedx/ngx-webstorage";

    selector: "my-component",
    templateUrl: "./my-component.html"
export class MyComponent implements OnInit {
    constructor(private _storage: LocalStorage) {}

    ngOnInit(): void {
        this._storage.onChange.subscribe(event => {
            console.log(`${event.key}: ${event.oldValue} => ${event.newValue}`);

        this._storage.set("foo", "bar"); // "foo: null => bar"
        this._storage.set("foo", "baz"); // "foo: bar => baz"
        this._storage.remove("foo"); // "foo: baz => null"

The values contained in the newValue and oldValue properties of the StorageEvent instances are the raw storage values. If you use the WebStorage.setObject() method to store a value, you will get the serialized string value, not the original value passed to the method:

this._storage.setObject("foo", {bar: "baz"});
// "foo: null => {\"bar\": \"baz\"}"

Changes in the context of another document

The LocalStorage and SessionStorage classes support the global storage events.

Everytime a change is made to the storage area within the context of another document (i.e. in another tab or <iframe>), a change event is emitted to notify the modification.


You do not need to explicitly subscribe to the global storage events: this is automatically done when instantiating the service. The subscription is canceled when the service is destroyed (i.e. its ngOnDestroy() method is called).