json中的日期数组如何循环

var jsonstr = "{'dateList':['2017-09-04','2017-09-05','2017-09-06','2017-09-07','2017-09-08','2017-09-09','2017-09-10']}";    //json字符串转换为json对象    var json = eval('(' + jsonstr + ')');    //取数组值    var arr = json.dateList;    //循环数组    $.each(arr, function(key, val) {        alert(arr[key]);//可以输出        //arr[1]    });