js 计算2个日期的天数

<SCRIPT language="javascript">

alert("111111111111111");

//+---------------------------------------------------
//| 求两个时间的天数差 日期格式为 YYYY-MM-dd
//+---------------------------------------------------
function daysBetween(DateOne,DateTwo)
{
var OneMonth = DateOne.substring(5,DateOne.lastIndexOf ('-'));
var OneDay = DateOne.substring(DateOne.length,DateOne.lastIndexOf ('-')+1);
var OneYear = DateOne.substring(0,DateOne.indexOf ('-'));

var TwoMonth = DateTwo.substring(5,DateTwo.lastIndexOf ('-'));
var TwoDay = DateTwo.substring(DateTwo.length,DateTwo.lastIndexOf ('-')+1);
var TwoYear = DateTwo.substring(0,DateTwo.indexOf ('-'));

var cha=((Date.parse(OneMonth+'/'+OneDay+'/'+OneYear)- Date.parse(TwoMonth+'/'+TwoDay+'/'+TwoYear))/86400000);
alert("4444444444444444444"+cha+"天");
return Math.abs(cha);
}

alert("4444444444444444444");
</SCRIPT>