code: function () {
              var _data = this._dataElement().data("bind");
              if (typeof _data == "string" && typeof ko == "object") {
                  var _vm = ko.dataFor(this._dataElement()[0]);
                  if (typeof _vm == "undefined") return true;
                  var _all = _data.split(","), _handler;
                  for (var i = 0; i < _all.length; i++) {
                      var d = _all[i].split(":");
                      if ($.trim(d[0]) == "value") {
                          _handler = $.trim(d[1]);
                          break;
                      }
                  }
                  if (_handler) {
                      this._isKO = true;
                      ko.computed(function () { this.option("value", _vm[_handler]()); }, this);
                  }
              }
          }
docs: Listener for KO binding