问对于nodejs中的每个模块需要一个通用的mongodb连接

EN

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";
var dbo;
MongoClient.connect(url, function(err, db) {
  if (err) throw err;
  dbo = db.db("mydb");
});

router.post('/', function(req, res) {

    dbo.collection("customers").find({"userid":req.body.userid}).toArray(function(err, result) {
    if (err) throw err;
    if(result.length>0){
        res.send("username already taken please enter differnt username ")
    }

    else if(req.body.fname==undefined||(!validator.isAlpha(req.body.fname))){
    res.send("please enter only alphabets as fname ")
   }

   else if(req.body.lname==undefined||(!validator.isAlpha(req.body.lname))){
    res.send("please enter only alphabets as lname ")
   }

   else if(req.body.userid==undefined||(!validator.isAlphanumeric(req.body.userid))){
    res.send("please enter only alphanemric as user name ")
   }

    else if(req.body.pwd==undefined||req.body.pwd.length<6){
    res.send("please enter atleast  6 charcaters as password ")
   }

   else{
            var bcrypt = require('bcryptjs');
            var salt = bcrypt.genSaltSync(10);
            var hash = bcrypt.hashSync(req.body.pwd, salt);
            req.body.pwd=hash;


        dbo.collection("customers").insertOne(req.body, function(err, res) {
        if (err) throw err;
        console.log("1 document inserted");
        });
        res.send(req.body);
    }

 });


    });



module.exports = router;