client/src/app/app.service.ts

   1 import { Injectable } from '@angular/core';
   2
   3 export type InternalStateType = {
   4   [key: string]: any
   5 };
   6
   7 @Injectable()
   8 export class AppState {
   9
  10   public _state: InternalStateType = { };
  11
  12   // already return a clone of the current state
  13   public get state() {
  14     return this._state = this._clone(this._state);
  15   }
  16   // never allow mutation
  17   public set state(value) {
  18     throw new Error('do not mutate the `.state` directly');
  19   }
  20
  21   public get(prop?: any) {
  22     // use our state getter for the clone
  23     const state = this.state;
  24     return state.hasOwnProperty(prop) ? state[prop] : state;
  25   }
  26
  27   public set(prop: string, value: any) {
  28     // internally mutate our state
  29     return this._state[prop] = value;
  30   }
  31
  32   private _clone(object: InternalStateType) {
  33     // simple object clone
  34     return JSON.parse(JSON.stringify( object ));
  35   }
  36 }