Using Firebase reauthenticate

The reauthenticate() method is called on a firebase.User, not on firebase.auth.Auth itself.

var user = firebase.app.auth().currentUser;
var credentials = firebase.auth.EmailAuthProvider.credential('[email protected]', 'firebase');
user.reauthenticate(credentials);

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Update (July 2017):

There are some breaking change in the 4.0 version of the Firebase Web SDK. From the release notes:

BREAKING: firebase.User.prototype.reauthenticate has been removed in favor of firebase.User.prototype.reauthenticateWithCredential.

As far as I can tell the reauthenticateWithCredentialis a drop-in replacement for the old method.

Here's some code that enabled users to (a) reauthenticate in Firebase and (b) change their passwords after reauthenticating for me. I researched for about an hour while writing this, so hopefully it saves someone a minute.

Wrote in VueJS:

changePassword() {
            let self = this; // i use "self" to get around scope issues
            var user = firebase.auth().currentUser;
            var credential = firebase.auth.EmailAuthProvider.credential(
                this.$store.state.userId, // references the user's email address
                this.oldPassword
            );

            user.reauthenticateWithCredential(credential)
                .then(function() {
                    // User re-authenticated.
                    user.updatePassword(self.newPassword) 
                        .then(function() {
                            console.log("Password update successful!");
                        })
                        .catch(function(error) {
                            console.log(
                                "An error occurred while changing the password:",
                                error
                            );
                        });
                })
                .catch(function(error) {
                    console.log("Some kinda bug: ", error);
                    // An error happened.
                });