after typing "node app" in command line, I got following:


Express server listening on port 3000 in development mode

/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/lib/utils.js:413
throw err;
^
Error: Uncaught, unspecified 'error' event.
at NativeConnection.EventEmitter.emit (events.js:73:15)
at Model.init (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/lib/model.js:554:31)
at exports.tick (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/lib/utils.js:408:16)
at Db.ensureIndex (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/db.js:1066:28)
at Db.indexInformation (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/db.js:1200:28)
at Cursor.toArray (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:124:30)
at Cursor.each (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:166:32)
at Cursor.nextObject.self.queryRun (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:441:39)
at Cursor.close (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:687:5)
at Cursor.nextObject.commandHandler (/Library/WebServer/Documents/node.js/book/chapter01/authentication/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:441:21)

Please help!