node cannot destructure property code example

Example: Cannot destructure property

var env = process.env.NODE_ENV; // 'dev' or 'test'

var dev = { app: { port: 3000 }, db: {user: '', pass: '', host: '', port: , name: '' }};

var test = { app: { port: 3000 }, db: {user: '', pass: '', host: '', port: , name: '' }};

var config = { dev, test };

module.exports = config[env];