为什么连接users这个文档连接了两次，最后返回错误信息

Question

.post(,(req,res){     = req..,         = req..,         = req.[],         = req..;     .();     (!=){         .();         req.(,);         res.()}     = .(),         = .(req..).();     = ({         :,         :,         :});     .(.,(err,user){         .();         (err){             .();             req.(,err);             res.();         }         (user){             .();             req.(,);             res.();}         .((err,user){             .();            (err){                req.(,err);                res.();}             req..= ;.(req..);             req.(,);             .();             res.();});     }); });.= (username,callback){     .();     .(username);   .((err,db){         .();         (err){             .();             callback(err);}         db.(,(err,collection){             .();             (err){                 .();                 .();                 callback(err);}             .();             collection.fineOne({: username,},(err,user){                 .();                 .();                 (err){                     callback(err);}                 .();                 callback(,user);});         });     }); };

Answer 1

你这代码没发看呀