jq元素拖拽

1 <script type="text/javascript">
2         $(function(){
3           $('#a1').mousedown(function(e){
4             var positionDiv = $(this).offset();
5             var distenceX = e.pageX -positionDiv.left;
6             var distenceY = e.pageY -positionDiv.top;
7             $(document).mousemove(function(e){
8               var x = e.pageX -distenceX;
9               var y = e.pageY -distenceY;
10               if(x<0){
11                 x=0;
12               }else if(x>$(document).width()-$('#a1').outerWidth(true)){
13                 x = $(document).width()-$('#a1').outerWidth(true);
14 }
15               if(y<0){
16                 y=0;
17               }else if(y>$(document).height()-$('#a1').outerHeight(true)){
18                 y = $(document).height()-$('#a1').outerHeight(true);
19 }
20               $('#a1').css({
21                 'left':x+'px',
22                 'top':y+'px'
23 });
24 });
25             $(document).mouseup(function(){
26               $(document).off('mousemove');
27 });
28 });
29 });
30 
31 </script>