js 日期相减得到天数

<script>
var sDate="2007-12-25";
var eDate="2008-01-02";
var sArr = sDate.split("-");
var eArr = eDate.split("-");
var sRDate = new Date(sArr[0], sArr[1], sArr[2]);
var eRDate = new Date(eArr[0], eArr[1], eArr[2]);

var day= (eRDate-sRDate)/(24*60*60*1000); // 天数

var month = parseInt(day/28);//月数，要考虑2月份

alert(day);

</script>