cb-mongoose-2.js

var User = require('route/to/models/User.js');

// Find a user by his ID
User.findById(<id>, function(error, user) {

   if (error) throw error;
   user.banned = true;

   // Save the changes
   user.save(function(error) {
     
      if (error) throw error;
      console.log(user banned!); 

   });
});