Passport.js Spotify Strategy - User.Save() is not a function

Question

I am trying to save the access as well as refresh tokens in my db to then make API calls for that user. I have followed the examples online as best I can for both Passport-js-spotify, JMPerez Passport Spotify example, and Spotify API documentation, but I still receive an error saying User.save() is not a function. I am able to retrieve the user information from the DB if I just findOne. Furthermore, I have a feeling that I am setting my callback up incorrectly as well. A little turned around with it all. I would greatly appreciate any help in resolving. I have included my code below. Please let me know if you need any additional information.

const express = require("express");
const router = express.Router();
const SpotifyStrategy = require("passport-spotify").Strategy;
const passport = require("passport");
const SpotifyUser = require("../Models/UserSpotify");

var spotifyID;

passport.use(
    new SpotifyStrategy({
        clientID: "84f1c0xxxx29b95xxx0b0fdxxx42f5ce",
        clientSecret: "0b0xxx5944ad8bxx07ab4xxxx",
        callbackURL: "http://localhost:3001/spotify/callback",
    }, function (accessToken, refreshToken, expires_in, profile, done) {

        spotifyID = profile.id
        displayName = profile.displayName
        email = profile._json.email
        profileURL = profile.profileUrl
        accessToken = accessToken
        refreshToken = refreshToken
        country = profile.country
        accountType = profile.product

        console.log(spotifyID)

        process.nextTick(function () {
            SpotifyUser.findOne({
                'spotifyID': spotifyID
            }).then((currentUser) => {
                if (!currentUser) {
                    const User = new SpotifyUser == ({
                        spotifyID: spotifyID,
                        displayName: displayName,
                        email: email,
                        profileURL: profileURL,
                        accessToken: accessToken,
                        refreshToken: refreshToken,
                        country: country,
                        accountType: accountType
                    })
                    User.save(function (err) {
                        if (err) console.log(err);
                        return done(err, user);
                    })
                } else {
                    console.log(currentUser);
                }
            })

        })


router.get(
    "/login",
    passport.authenticate(
        "spotify", {
            scope: ["user-read-email", "user-read-private"],
            showDialog: true,
        }
    ),
    function (req, res) {
        console.log(res.accessToken)
        console.log(res.refreshToken)
    }
);

router.get(
    "/callback",
    passport.authenticate("spotify", {
        failureRedirect: "/login"
    }),
    function (req, res) {
        // Successful authentication, redirect home.
        res.redirect("/success");

    }
);

router.get("/success", passport.authenticate('spotify'), (req, res) => {
    res.send("success")

});

Answer 1

One obvious thing I see in code is

 const User = new SpotifyUser == ({
                        spotifyID: spotifyID,
                        displayName: displayName,
                        email: email,
                        profileURL: profileURL,
                        accessToken: accessToken,
                        refreshToken: refreshToken,
                        country: country,
                        accountType: accountType
                    })

Remove the ==

const User = new SpotifyUser({
                        spotifyID: spotifyID,
                        displayName: displayName,
                        email: email,
                        profileURL: profileURL,
                        accessToken: accessToken,
                        refreshToken: refreshToken,
                        country: country,
                        accountType: accountType
                    })