分配对象分配给另一个对象时突然变成空白

Question

我有这个代码...

var Sequelize = require('sequelize');
var sequelize = null;

if (process.env.HEROKU_POSTGRESQL_BROWN_URL) {
    // the application is executed on Heroku ... use the postgres database
    sequelize = new Sequelize(process.env.HEROKU_POSTGRESQL_BROWN_URL, {
        dialect: 'postgres',
        protocol: 'postgres',
        port: match[4],
        host: match[3],
        logging: true //false
    })
} else {
    // the application is executed on the local machine ... use mysql
    sequelize = new Sequelize('ticketing', 'root',null,{
        dialect: 'mysql'
    });
    console.log(typeof sequelize);
}

var db = {};
db.Sequelize =  Sequelize;
db.sequelize = sequelize;
db.User = sequelize.import(__dirname + '/User');
console.log(typeof db.sequelize);
module.exports = db;

通常此代码应在控制台中显示两个对象，对吗？但是控制台中只有一个对象，第二个对象却奇怪地不显示任何内容，无论是null还是未定义。这里发生了什么？另外，当我尝试db.sequelize.define（某些代码）时，会抛出一个错误，即未定义define。