Load angular app from localhost, and fallback to a static resource

LoadAngularFromLocalhost.js

var j$ = jQuery.noConflict();

if ({! debugEnabled }) {
  loadSourcesLocalhost().fail(loadSourcesSfdc);
} else {
  loadSourcesSfdc();
}

function loadSourcesLocalhost() {
  return j$.ajax({url: '//localhost:3000/vendor.js', dataType: 'script', timeout: 100})
    .done(function () {
      console.log("using localhost");
      var src = {
        styles: "//localhost:3000/styles.css",
        app: "//localhost:3000/app.js"
      };
      return loadSource(src);
    });
}

function loadSourcesSfdc() {
  console.log("using salesforce");
  var src = {
    app: "{! URLFOR( $Resource.ngApp, 'js/app.js' ) }"
  };
  return j$.getScript("{! URLFOR( $Resource.ngApp, 'js/vendor.js' ) }")
   .then(function() {
    return loadSource(src);
   });
}

function loadSource(src) {
  if (src.styles) {
    j$('head').append(createStylesheet(src.styles));
  }
  return j$.getScript(src.app)
  .then(function(){
    angular.bootstrap(document, ['app']);  
  });
}

function createStylesheet(src) {
  var style = document.createElement("link");
  style.rel = "stylesheet";
  style.href = src;
  return style;
}