JavaScript 计算两个时期之间的天数

//+---------------------------------------------------
//| format: 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);
    return Math.abs(cha);
}