Firebase Onauthstatechanged Error With React

I'm trying to check if a user is logged in or not on my React webpage using Firebase, however I keep getting an error TypeError: Cannot read property 'onAuthStateChanged' of undefi

Solution 1:

You need to include firebase package

import firebase from"firebase";

and then use auth() function of firebase

authListener() {
firebase.auth().onAuthStateChanged((user) => {
  if (user) {
    this.setState({ user })
  } else {
    this.setState({ user: null })
  }
})}

if you are importing firebase from another file then configure it like this

import firebase from'firebase/app';
import'firebase/auth';
exportconstinit = () => {
    let config = {
        apiKey: "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
        authDomain: 'xxxxxxxxxxxxx'
    };
    firebase.initializeApp(config);
};

exportconst firebaseAuth = firebase.auth;