为什么我的警报在javascript中显示未定义

var database = require('../../db');
var rightponame = '1';
var rightdevname = '';
var rightpopassword = '';
var rightdevpassword = '';
database.db.once('open', function() {
  console.log('success');

  var cursor = database.db.collection('user').find({}, {
    _id: 0
  });
  cursor.each(function(err, doc) {
    if (doc != null) {
      rightponame = doc.productOwner;
      rightdevname = doc.developer;
      rightpopassword = doc.popassword;
      rightdevpassword = doc.devpassword;
      console.log(rightponame);
      console.log(rightdevname);
      console.log(rightpopassword);
      console.log(rightdevpassword);
    } else {
      console.log('o');
    }
  });


});

function login() {
  var getusername = document.getElementById("username").value;
  var getpassword = document.getElementById("password").value;

  alert(rightponame);

}
var database = require('../../db');
var rightpo