throw new MongooseError('Model.prototype.save() no longer accepts a callback'); ....... Fixing use then and catch instead of use if and else method

[UmitRock]

use new code of register post

app.post("/register", function(req, res) {
const newUser = new User({
email: req.body.username,
password: req.body.password
});

newUser.save().then(function(){
res.render("secrets");
}).catch(function (err){
console.log(err);
});
});

---

instead of old code of register post

app.post("/register", function(req, res){
const newUser = new User({
email: req.body.username,
password: req.body.password
});
newUser.save(function(err){
if (err) {
console.log(err);
} else {
res.render("secrets");
}
});
});