authentication - Logout BasicAuth in node.js -

i have reference http://blog.modulus.io/nodejs-and-express-basic-authentication

my code conect database mongodb:

var admin = express.basicauth(authentikasi); function authentikasi(user, pass, callback) {      // declrare database mongodb     db.collection('ak_admin', function (err, data) {         data.findone({'adm_name': {'$regex': user}}, function (err, level) {             if (level == null) {                 console.log('nilai database administrator masuk null ulangi login');                 callback(null);              } else {                 var = level.adm_name;                 var b = level.adm_password;                 var c = level.adm_mobile;                   if (user === && pass === b) {                     callback(null, {name: a, id: c});                } else                     callback(null, false);             }         });     }); };    app.get('/admin', admin, function(req, res){         res.sendfile(__dirname + '/admin/index.html'); });  

my schema login basicauth succesfull question : how create logout because site admin have login after use schema not input username , password again :

    app.get('/logout', function(req, res){     //how code in here erase memory in variable admin (user , pass)            res.sendfile(__dirname + '/public/index.html');  }); 

please me you...