Class: Def

// https://some.cdn/js/just.js
window.just = {'Define': function () {}};

// index.html
< !DOCTYPE html>
< html data-just-Define='{"main": "/js/main.js"}'>
< head>
   < title>Test</title>
   < script src='https://some.cdn/js/just.js' async></script>
< /head>
< body>
< /body>
< /html>

// /js/main.js
just.Define.configure({
   'globals': {
       // Set justJs to window.just
       'justJs': function () { return just; }
   },
   'urls': {
       // Load "/css/index.css" when "index.css" is required.
       'index.css': '/css/index.css'
   },
   'nonScripts': {
       // Call when "main.html" is required.
       'main.html': function () { return '<main></main>'; }
   }
});

// Load when document, justJs and index.css are ready:
just.Define('main', ['justJs', 'index.css'], function (j) {

   if (j.supportsTouch()) {
       j.Define('mobile', 'https://example/m');
       return;
   }

   j.Define('non-mobile', ['main.html']);

});

// Call only if j.supportsTouch()
just.Define(['mobile'], function (url) {
   window.redirect = url;
});

// Call when main.html is ready.
just.Define(['non-mobile'], function (html) {
   document.body.innerHTML = html;
});