js实现的左右选择框

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
sortitems = 1; // Automatically sort items within lists? (1 or 0)

function move(fbox,tbox) {
for(var i=0; i<fbox.options.length; i++) {
    if(fbox.options[i].selected && fbox.options[i].value != "") {
     var no = new Option();
     no.value = fbox.options[i].value;
     no.text = fbox.options[i].text;
     tbox.options[tbox.options.length] = no;
     fbox.options[i].value = "";
     fbox.options[i].text = "";
        }
   }
BumpUp(fbox);
if (sortitems) SortD(tbox);
}

    function moveall(fbox,tbox) {
for(var i=0; i<fbox.options.length; i++) {
    if(fbox.options[i].value != "") {
     var no = new Option();
     no.value = fbox.options[i].value;
     no.text = fbox.options[i].text;
     tbox.options[tbox.options.length] = no;
     fbox.options[i].value = "";
     fbox.options[i].text = "";
        }
   }
BumpUp(fbox);
if (sortitems) SortD(tbox);
}


function BumpUp(box)   {
for(var i=0; i<box.options.length; i++) {
    if(box.options[i].value == "")   {
       for(var j=i; j<box.options.length-1; j++)   {
        box.options[j].value = box.options[j+1].value;
        box.options[j].text = box.options[j+1].text;
        }
     var ln = i;
    break;
        }
   }
if(ln < box.options.length)   {
   box.options.length -= 1;
   BumpUp(box);
      }
}

function SortD(box)   {
var temp_opts = new Array();
var temp = new Object();
for(var i=0; i<box.options.length; i++)   {
temp_opts[i] = box.options[i];
}

for(var x=0; x<temp_opts.length-1; x++)   {
   for(var y=(x+1); y<temp_opts.length; y++)   {
     if(temp_opts[x].text > temp_opts[y].text)   {
      temp = temp_opts[x].text;
      temp_opts[x].text = temp_opts[y].text;
      temp_opts[y].text = temp;
      temp = temp_opts[x].value;
      temp_opts[x].value = temp_opts[y].value;
      temp_opts[y].value = temp;
         }
       }
}

for(var i=0; i<box.options.length; i++)   {
box.options[i].value = temp_opts[i].value;
box.options[i].text = temp_opts[i].text;
     }
}




  
// End -->
</script>

<form ACTION="" METHOD="POST">
<table border="0">
<tr>
<td><select multiple size="7" name="list1" style="width:250px">
<option value="11"> item 1.1 </option>
<option value="12"> item 1.2 </option>
<option value="13"> item 1.3 </option>
</select></td>
<td>
<input type="button" value="    >>   " onclick="moveall(this.form.list1,this.form.list2)" name="B3">
<br/>
<input type="button" value="    >   " onclick="move(this.form.list1,this.form.list2)" name="B1">
<br/>
<input type="button" value="    <   " onclick="move(this.form.list2,this.form.list1)" name="B2">
<br/>

<input type="button" value="    <<   " onclick="moveall(this.form.list2,this.form.list1)" name="B4">
</td>
<td><select multiple size="7" name="list2" style="width:250px">
<option value="21"> item 2.1 </option>
<option value="22"> item 2.2 </option>
<option value="23"> item 2.3 </option>
</select></td>


</tr>
</table>
</form>