JavaScript实现点击文本自动定位到下拉框选中操作

<html >
 
<head runat="server">
 <title></title>
 <style type="text/css">
  #SiteStat
  {
   width: 97px;
   height: 181px;
  }
 </style>
</head>
<body>
 <from>
 <script language=javascript>
  function foo(){
   //var i = 3;
   var i = document.getElementById("ds").value;
   o = document.getElementById("SiteStat");
   for (c = 0; c < o.length; c++) {
    dy = o.options[c].value.indexOf(i)
    
    if(dy==0)
    //if (o.options[c].value == i) 
    {
     o.options[c].selected = true;
     break;
    }
   }
  }
</script>
 
<select name="SiteStat" multiple="multiple" class="select1" id="SiteStat">
 <option value="-1" selected></option>
 <option value="1" >状态A</option>
 <option value="0">状态B</option>
 <option value="22">状态C</option>
 <option value="33">状态D</option>
</select>
</from>
<input type='text' name='olala' id='ds'/>
<input type='submit' name='sub' value='查询显示' onclick="foo()"/>
</body>
</html>