how to get particular fields and update that fileds from database in route in nodejs?

i want to get username,email,password from database and update the passsword field,
i have code: router.put('/forget/:username',function(req,res){ User.findOneAndUpdate({ $or:[{username:req.params.username},{username:req.params.email} ] },{ "$set": {password: req.body.password}},(function(err, user){ var a = new User({ username :req.body.username, email :req.body.email, password :req.body.password }) if(err) { console.log(err); res.status(500).send(err); } else { res.status(200).send(user); } })); });

via Poonam