docs: function () {
                  if (!_placeholderSupported && this._cfg.placeholder) {
                      var element = this._domElt;
                      if (element.value === "") {
                          element.value = this._cfg.placeholder;
                          var cssClass = new aria.utils.ClassList(element);
                          cssClass.add('placeholder');
                          cssClass.$dispose();
                          if (this._hasFocus) {
                              ariaUtilsCaret.setPosition(element, 0, 0);
                          }
                          this._hasPlaceholder = true;
                          this._domElt.unselectable = "on";
                      }
                  }
              }