import { Injectable } from '@angular/core'; @Injectable() export class AppState { _state = { }; constructor() { ; } // already return a clone of the current state get state() { return this._state = this._clone(this._state); } // never allow mutation set state(value) { throw new Error('do not mutate the `.state` directly'); } get(prop?: any) { // use our state getter for the clone const state = this.state; return state.hasOwnProperty(prop) ? state[prop] : state; } set(prop: string, value: any) { // internally mutate our state return this._state[prop] = value; } _clone(object) { // simple object clone return JSON.parse(JSON.stringify( object )); } }