<%
String path = request.getContextPath();
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html>
<head>
<script type="text/javascript" src="<%=path%>/dwr/engine.js"></script>
<script type="text/javascript" src="<%=path%>/dwr/util.js"></script>
 <script type="text/javascript"> 
function f()

DwRUtil.removeallopions("selectTest");
DWRUtil.addOptions("selectTest", [
  { name:'Africa', population:'800m' },
  { name:'America', population:'900m' },
  { name:'Asia', population:'3000m' },
  { name:'Australasia', population:'31m' },
  { name:'Europe', population:'700m' }
],"population");
DWRUtil.setValue($(txtname),"dai");
 DWRUtil.debug($(txtname).value);  
return false;
}
</script>
</head>
<body>  
<select id="selectTest">
<option>
asdf
</option>
<option>
aasdf
</option>
</select>
<input type=text id=txtname>
<input type=button onclick="f()">
<br>
</body>
</html>去掉DwRUtil.removeallopions("selectTest"); 页面可以增加opions,
不去掉DwRUtil.removeallopions("selectTest");整个页面没有任何效果,请问各位大侠,为什么呢?