code: function(_document,_force){
                  var _r = _getSelectionRange(_document);
                  if (_force || !_sameRange(_r, _ranges.get(_document))) {
                      _ranges.set(_document, _r);
                      setTimeout(function(){
                          console.log('selectionchange')
                          _v._$dispatchEvent(_document,'selectionchange');
                      }, 0);
                  }
              }
docs: 触发selectionchange
  @param {Object} _document 文档对象
  @param  {Event} _event 事件对象