[javascript] 파이어베이스 회원가입/로그인 성공 여부 체크 방법

irebase.auth().signInWithEmailAndPassword(email, password).then(function(user) {
   // user signed in
}).catch(function(error) {
    var errorCode = error.code;
    var errorMessage = error.message;

    if (errorCode === 'auth/wrong-password') {
        alert('Wrong password.');
    } else {
        alert(errorMessage);         
    }
    console.log(error);
});

reference : https://stackoverflow.com/questions/39958467/firebase-authentication-javascript-get-success