dojo远程异步调用问题

[hnsongbiao]

<script src="http://ajax.googleapis.com/ajax/libs/dojo/1.9.0/dojo/dojo.js"></script>

   script.get({
		url: "http://gc.ditu.aliyun.com/geocoding/",
		content: {a:"北京市丰台区新发地"},
		handleAs: "json"
		//callbackParamName: "callback"
			}).then(function(res){
                        alert(res)
			var description = "";
			for(var i in res){  
				var property=res;  
				description+=i+" = "+property+"\n"; 
			}   
			alert(description);
			});

返回的结果

args = [object Object]
url = http://gc.ditu.aliyun.com/geocoding/?a=%E5%8C%97%E4%BA%AC%E5%B8%82%E4%B8%B0%E5%8F%B0%E5%8C%BA%E6%96%B0%E5%8F%91%E5%9C%B0
query = null
handleAs = json
id = dojoIoScript2
canDelete = false
jsonp = undefined
requestId = dojo_request_script1
scriptId = undefined

应该返回的res数据是：

{"cityName":"","address":"北京市,北京城区,丰台区,","level":3,"alevel":3,"lat":39.85847,"lon":116.28706}

通过dojo异步调用阿里云地图数据，为何出错呢？
为何会返回这些呢？