ajax连续提交ajax请求返回结果不正常 请问应该怎么改

[糊涂娃8343]

调用方法1：结果正确
<input type="button" value="测试" onclick="test()">

function test() {
if(index<2)
index++;
else
index=0;

var arr=[2050,2049,2052];
getItemStr(arr[index]);
}
---------------------------------------------------------------------------------------------------
调用方法2：结果就不正常
window.onload=function () {
getItemStr(2050);
getItemStr(2049);
getItemStr(2048);

for (var i=0;i<arr.length;i++)
{
getItemStr(arr[i]);
}
}
------------------------------------------------------------------------------------------------------------
以下是被调用方法：
function getItemStr(orderid) {
var itemStr="";
$.ajax({
url:"http://127.0.0.1:1337/getOrder",
dataType:"jsonp",
data:{"state":0,"orderid":orderid},
type:"get",
async:false,
jsonpCallback:"success_jsonpCallback",
success:function (goodsSet) {

$.each(goodsSet,function (idx,goods) {

itemStr+="<ion-item class=\"item-avatar item-stable mydefine item\">";
itemStr+="<img src=\"http://image-zm.oss-cn-beijing.aliyuncs.com"+goods.goods_image+"\">";

itemStr+="<h2>"+goods.goods_name+"</h2>";
itemStr+="<p class=\"b9232e price\">￥"+goods.goods_price+"";
itemStr+="<a href=\"javascript:void(0)\">x"+goods.goods_num+"(发货)x0(仓储)</a>";
itemStr+="</p>";
itemStr+="</ion-item>";
})
alert(itemStr);

},
error:function (XMLHttpRequest, textStatus, errorThrown) {
alert("查询订单商品失败："+XMLHttpRequest.status+"------"+textStatus);
}
});

}