prototype中的ajax异步加载

jquery前台处理：	
var param = {a:a};
$.post("*.do",param,function(data) {
    var columHtml =  "";
    $.each(data, function(i, item) {
	columHtml = columHtml + "<option value='"+item[0]+"'>"+item[1]+"</option>"
    });   				     			
    $("#columnid").append(columHtml);						 		
 });
后台：返回json 格式

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prototype.js使用ajax级联:
后台返回json格式的list,前台使用ajax 处理json 和 list 

前台页面：
<select name="id" id="id"  onchange="aa(this.value)">
	<option value="0">请选择</option>							
</select>

js方法
function  aa(id){
		function onSuccess(response) {
			var data = response.responseText.evalJSON();  
			var colList = data.dataList;
			var columHtml =  "";
			for(var i = 0;i<colList.length;i++){
				columHtml = columHtml + "<option value='"+colList[i].id+"'>"+colList[i].colName+"</option>"
			}			   	
			alert(columHtml);	
			var a = $('columnid');
			alert(a.innerHTML);
  			$('columnid').innerHTML = columHtml;							
        }
		function onFailure(response) { 
			alert('数据请求异常');
        }
		var params = "&websiteId="+websiteid;
		ajax = new Ajax.Request(
				'a.do',{
				method: 'POST',
				asynchronous: true,
				parameters:params,
				onSuccess : onSuccess,
				onFailure : onFailure 
			}
		);     	
	}


后台action处理：

	JSONObject jsonObject = new JSONObject();
	jsonObject.put("dataList", maplist);  
	this.getPrintWriter(jsonObject);

xml处理：
<action name="a" class="AAction"  method="a">
<result name="success" type="json"></result>
</action>