wrap or leak, sync or async

loadScript.js

;(function () {

  var loadScript = (function () {

    var debug = typeof debug !== 'function' ? function (text) {
      console.log(text);
    } : debug;

    var wrapAsync = function (url, doc, win) {
      debug('load script: (safe and async) ' + url);
      $.ajax({
        url: url,
        dataType: 'text',
        success: function (result) {
          var func;
          func = new Function('document', 'window', result);
          func(doc, win);
        }
      });
    };

    var wrapSync = function (url, doc, win) {
      debug('load script: (safe and sync) ' + url);
      $.ajax({
        url: url,
        dataType: 'text',
        success: function (result) {
          var func;
          func = new Function('document', 'window', result);
          func(doc, win);
        },
        async: false
      });
    };

    var leakAsync = function (url) {
      debug('load script: (leak and async) ' + url);
      script = document.createElement('script');
      script.src = url;
      document.getElementsByTagName('body')[0].appendChild(script);
    };

    var leakSync = function (url) {
      debug('load script: (leak and sync) ' + url);
      document.write('<script src="' + url + '"><\/script>');
    };

    var load = function (url, options) {
      var defaults = {
        win: {},
        doc: {},
        sync: false
      };
      var isWrap, isSync, win, doc;
      options = typeof options === 'undefined' ? {} : options;
      isWrap = typeof options.win !== 'undefined' || typeof options.doc !== 'undefined';
      isSync = typeof options.sync === 'undefined' ? defaults.sync : options.sync;
      if (isWrap) {
        win = typeof options.win === 'undefined' ? defaults.win : options.win;
        doc = typeof options.doc === 'undefined' ? defaults.doc : options.doc;
      }
      if (isWrap && isSync) {
        return wrapSync(url, doc, win);
      }
      if (isWrap && !isSync) {
        return wrapAsync(url, doc, win);
      }
      if (!isWrap && isSync) {
        return leakSync(url);
      }
      if (!isWrap && !isSync) {
        return leakAsync(url);
      }
    };

    return load;

  })();

  window['loadScript'] = loadScript;

})();