This method will simply return an array containing all the keys in the store. This will come in handy later when we work on the UI, in order to allow us to load the existing collections.

The following is the relevant code:

getMediaCollectionIdentifiersList(): Promise<string[]> { 
    return new Promise<string[]>((resolve, reject) => { 
        console.log("Retrieving the list of media collection 
        identifiers"); 
        this._store.keys().then(keys => { 
            console.log(`Retrieved the of media collection
             identifiers: 
            ${keys}`); 
            resolve(keys); 
        }) 
        .catch(err => { 
            console.error(`Failed to retrieve the list of media 
            collection identifiers. Error: ${err}`); 
            reject(err); 
        }) 
    }); 
} 

This is, of course, very similar to what we've just done in the preceding section. The main difference the following is that we use the keys() method, which returns the list of keys, as described in the localForage documentation: https://localforage.github.io/localForage/#data-api-keys.