js怎么引入js，如下文中，js/abc.js 这样无法生效？这要怎么做才可以？
document.writeln("<!DOCTYPE html>");
document.writeln("<html>");
document.writeln(" <head>");
document.writeln(" <meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />");
document.writeln(" <meta http-equiv=\"Content-Type\" content=\"text/html; charset=gb2312\" />");
document.writeln(" <meta name=\"viewport\" content=\"width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0\">");
document.writeln(" <meta name=\"applicable-device\" content=\"mobile\">");
document.writeln(" <meta name=\"apple-mobile-web-app-capable\" content=\"yes\">");
document.writeln(" <meta name=\"apple-mobile-web-app-status-bar-style\" content=\"black\">");
document.writeln(" <meta http-equiv=\"X-UA-Compatible\" content=\"ie=edge\">");
document.writeln(" <title></title>");
document.writeln(" </head>");
document.writeln(" <body>");
document.writeln(" <div>");
document.writeln(" 你好，欢迎您光临！！！");
document.writeln(" </div>");
document.writeln(" <script src=\"js/abc.js\" type=\"text/javascript\"></script>");
document.writeln(" </body>");
document.writeln("</html>");
document.writeln("");
