function getByIndex<T>(db: IDBDatabase, storeName: string, indexName: string, key: any): Promise<T[]> {
	let results = [];
	return new Promise<T[]>((resolve, reject) => {
		const transaction = db.transaction(storeName, 'readonly');
		const store = transaction.objectStore(storeName);
		const index = store.index(indexName);
		//on peut aussi faire index.get si on souhaite lire qu'une seule valeur
		const request = index.openCursor(key);
		request.onsuccess = (event: any) => {
			const cursor = event.target.result;
			if (cursor) {
				results.push(cursor.value);
				cursor.continue();
			} else {
				resolve(results);
			}
		};
		request.onerror = (event: any) => {
			reject(event.error);
		};
	});
}