Bootstrap的modal拖动效果如何？

(function(){
 function moveModal($this){
  var $head = $this.find('.modal-header');
  var $dialog = $this.find('.modal-dialog');
  var move = {
   isMove: false,
   left: 0,
   top: 0
  };
  //委托
  console.log('点击的是',$this);
  $this.on('mousemove', function(e){
   if(!move.isMove) return;
   console.log('移动的是', e.target);
   $dialog.offset({
    top: e.pageY - move.top,
    left: e.pageX - move.left
   });
  }).on('mouseup', function(e){
   move.isMove = false;
  });
  $head.on('mousedown', function(e){
   move.isMove = true;
   var offset = $dialog.offset();
   move.left = e.pageX - offset.left;
   move.top = e.pageY - offset.top;
  });
 }
 var oldModal = $.fn.modal;
 $.fn.modal = function(o, _r){
  var $this = $(this);
  if(!$this.attr('ifbindmv')){
   $this.attr('isbindmv','1');
   moveModal($this);
  }
  return oldModal.call(this, o, _r);
 }
 ////要拖动的div背景
 //$('#showErr').modal({backdrop: 'static'});
})();