Angular - Ionic | Storage service using @ionic/storage. Wich is a reasonable abstraction to use IndexedDB

storage.service.ts

import { Injectable } from '@angular/core';
import { APP_CONSTANTS } from '@constants/app.constants';
import { Storage } from '@ionic/storage';

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

    private _storage: Storage | null = null;

    constructor(private ionStorage: Storage) {
        this.init();
    }

    async init() {

        if (this._storage != null) {
            return;
        }
        const storage = await this.ionStorage.create();
        this._storage = storage;

        const createdAt = <string>await this._storage.get(APP_CONSTANTS.DB_EXIST_FLAG);

        if (!createdAt) {
            this._storage.set(APP_CONSTANTS.DB_EXIST_FLAG, new Date().toLocaleString());
        }
    }

    /**
     * Get the value associated with the given key
     * @param key Any key will be juntioned with the APP_PREFIX constant
     */
    async get(key: string): Promise<any> {

        // return this.storage.get(`${APP_CONSTANTS.APP_PREFIX}-${key}`)
        //     .then(data => data)
        //     .catch(e => { throw e; })

        await this.init();
        return await this._storage?.get(`${APP_CONSTANTS.APP_PREFIX}-${key}`);
    }

    /**
     * Set the value for the given key
     * @param key Any key will be juntioned with the APP_PREFIX constant
     * @param value Any value will be stringified
     */
    async set(key: string, value: any): Promise<any> {
        // return this.storage.set(`${APP_CONSTANTS.APP_PREFIX}-${key}`, value)
        //     .then(() => true)
        //     .catch(e => { throw e });

        await this.init();
        return await this._storage?.set(`${APP_CONSTANTS.APP_PREFIX}-${key}`, value);
    }

    /**
     * Returns a promise that resolves with an object Keys that has an 
     * array of strings (keys names)
     */
    async keys(): Promise<string[]> {

        await this.init();
        return await this._storage?.keys();
    }

    /**
     * Returns a promise that resolves with the number of keys stored
     */
    async length(): Promise<number> {

        await this.init();
        return await this._storage?.length();
    }

    /**
     * Remove any value associated with the given key
     * @param key 
     */
    async remove(key: string): Promise<void> {

        await this.init();
        return this._storage.remove(`${APP_CONSTANTS.APP_PREFIX}-${key}`)
            .then(() => console.log(`Value: ${key} removed from the Storage`))
            .catch(e => { throw e; })
    }

    /**
     * Remove ALL key value pair stored. WARNING: This can't be undone.
     */
    async removeAll(): Promise<void> {

        await this.init();

        if(confirm('DELETE app Storage data? (cannot be reversed)')){
            return this._storage.clear()
                .then(() => { 
                    console.log('Storage Deleted');  
                    alert("Storage Deleted")
                })
                .catch(e => { throw e; })
        } else {
            return null;
        }

    }


}