import { NgForageConfig } from 'ngforage';
...

@NgModule({
  ...
})
export class AppModule {
  public constructor(
    ngfConfig: NgForageConfig
  ) {
    ngfConfig.configure({
      name: 'myProject',
      driver: [ // optional - defaults to indexedDB -> webSQL -> localStorage -> sessionStorage
        NgForageConfig.DRIVER_INDEXEDDB,
        NgForageConfig.DRIVER_LOCALSTORAGE
      ]
    });
  }
}

import { Injectable, OnInit } from '@angular/core';
import { CachedItem, NgForage, NgForageCache, NgForageConfig } from 'ngforage';
import { Observable, from } from 'rxjs';

@Injectable({
	providedIn: 'root'
})
export class StorageService implements OnInit {

	constructor (
          private readonly ngf: NgForage,
          private readonly cache: NgForageCache
        ) { }

	public getItem<T> (key: string): Observable<T> {
		return from(this.ngf.getItem<T>(key));
	}

	public setItem<T> (key: string, data: T): Observable<T> {
		return from(this.ngf.setItem<T>(key, data));
	}

	public removeItem (key: string): Observable<void> {
		return from(this.ngf.removeItem(key));
	}

	public removeAll (): Observable<void> {
		return from(this.ngf.clear());
	}

	public getCachedItem<T> (key: string): Observable<T | null> {
		return from(this.cache.getCached<T>(key)
			.then((r: CachedItem<T>) => {
				if (!r.hasData || r.expired) {
					return null;
				}

				return r.data;
			}));
	}

	public setCachedItem<T> (key: string, data: T): Observable<T> {
		return from(this.cache.setCached<T>(key, data));
	}

	public ngOnInit (): void {
		this.ngf.name = 'myApp';
		this.cache.driver = NgForageConfig.DRIVER_SESSIONSTORAGE;
	}
}