I have a problem with firebase. I'm getting this error: Uncaught TypeError: Failed to resolve module specifier "firebase/app". Relative references must start with either "/", "./", or "../". app.js:

import * as firebase from 'firebase/app';
import { Menu } from './Menu.js';
import { UserManagment } from './UserManagment.js';
const firebaseConfig = {
    apiKey: '[apiKey]',
    authDomain: '[authDomain]',
    projectId: '[projectId]',
    storageBucket: '[storageBucket]',
    messagingSenderId: '[messagingSenderId]',
    appId: '[appId]',
    measurementId: '[measurementId]',
};
const app = firebase.initializeApp(firebaseConfig);

In the firebaseConfig object are valid properties copied from firebase site. I installed firebase by npm.