When the user signs up the display name doesn't save.

I tried to make a login system and all works fine until the displayName (see below).

Can anyone tell me what I am doing wrong?

function signUp() {
    // Fetching value from a html input fields with id
    const email = document.getElementById("email").value;
    const password = document.getElementById("password").value;

    // Fetching additional informations
    const displayName = document.getElementById("displayName").value;

    // Performing Sign Up Operation
    firebase.auth().createUserWithEmailAndPassword(email, password);

    user.updateProfile({

        displayName: displayName

    });
};