js怎样读取json里面的数据 ：

json数据如下：要求获取afsServiceId 的值

var jsonStr = {"success":true,"resultMessage":"","resultCode":"0","result":{"serviceInfoList":[{"afsServiceId":283705344,"customerExpect":10,"customerExpectName":"退货","afsApplyTime":"2017-03-07 10:02:15","orderId":50654723050,"wareId":1487981,"wareName":"北美电器（ACA）搅拌器 榨汁机 果汁机 婴儿辅食机AF-OR01 ","afsServiceStep":21,"afsServiceStepName":"客服审核","cancel":0}],"totalNum":1,"pageSize":100,"pageNum":1,"pageIndex":1}}

//(1)获取afsServiceId的数据如下：
var obj = new Function("return" + jsonStr)();//转换后的JSON对象
//或者var obj=JSON.parse(jsonStr);//转换后的JSON对象
var afsServiceId = obj.result.serviceInfoList[0].afsServiceId;//服务端号
alert(afsServiceId);  //值为283705344

//(2)获取resultCode的值如下：
var obj = new Function("return" + jsonStr)();//转换后的JSON对象
var code = obj.resultCode;//服务端号
alert(code);  //值为0