Uncaught FirebaseError: Firebase: Firebase App named '[DEFAULT]' already exists (app/duplicate-app). javascript code example

Example 1: Firebase: Firebase App named '[DEFAULT]' already exists

if (!firebase.apps.length) {
   firebase.initializeApp({});
}else {
   firebase.app(); // if already initialized, use that one
}

Example 2: Firebase: Firebase App named '[DEFAULT]' already exists

if (!firebase.apps.length) {
    firebase.initializeApp({});
}