我试图用nowjs启动node.js服务器，但是我收到以下错误：
/var/www/vhosts/sitename.com/httpdocs/sitename/assets/js/node_modules/now.js:2
TagName("head")[0].appendChild(fileref)}return nowObjects[uri]=now};window.now
^
ReferenceError: window is not defined
at /var/www/vhosts/sitename.com/httpdocs/sitename/assets/js/node_modules/now.js:2:9761
at Object. (/var/www/vhosts/sitename.com/httpdocs/sitename/assets/js/node_modules/now.js:2:9794)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.require (module.js:362:17)
at require (module.js:378:17)
at /var/www/vhosts/sitename.com/httpdocs/sitename/assets/js/app.js:35:14
at Object. (/var/www/vhosts/sitename.com/httpdocs/sitename/assets/js/app.js:38:3)