code: function() {
      var i, jsDir, jsPath, scripts = _document.getElementsByTagName("script");
      for (i = scripts.length; i--; ) {
        if (!(jsPath = scripts[i].src)) {
          jsDir = null;
          break;
        }
        jsPath = _getDirPathOfUrl(jsPath);
        if (jsDir == null) {
          jsDir = jsPath;
        } else if (jsDir !== jsPath) {
          jsDir = null;
          break;
        }
      }
      return jsDir || undefined;
    }
docs: Get the unanimous parent directory of ALL script tags.
  If any script tags are either (a) inline or (b) from differing parent
  directories, this method must return `undefined`.
  
  @returns String or `undefined`
  @private