var lastInsertId;
loginData={
        userName: req.body.txtUsername,
        password: req.body.txtPassword,
        active:1,
        createdOn:new Date(),
        updatedOn:new Date()
    };
var dbo = db.db("test");
dbo.collection("login").insertOne(loginData, function(err, result) {
        if (err) throw err;
        lastInsertId=result.insertedId;
});

if(lastInsertId){
            usersData={
                email: req.body.txtEmail,
                firstName: req.body.txtFirstName,
                lastName:req.body.txtLastName,
                mobileNumber:req.body.txtMobileNumber,
                login_id:lastInsertId,
                active:1,
                createdOn:new Date(),
                updatedOn:new Date()
            };

            dbo.collection("users").insertOne(usersData, function(err, result) {
                if (err) throw err;
                console.log('saved to users');
                });
        }