js method to compare date size_javascript skills

function DateDiff(d1,d2){
 var result = Date.parse(d1.replace(/-/g,"/"))- Date.parse(d2.replace(/-/g,"/"));
 return result;
}
function DateDiff(d1,d2){    
    start_at = new Date(d1.replace(/^(\d{4})(\d{2})(\d{2})$/,"$1/$2/$3"));
    end_at = new Date(d2.replace(/^(\d{4})(\d{2})(\d{2})$/,"$1/$2/$3"));
    if(start_at > end_at) {
      return false;
    }
    return true;
}
//js获取当前日期
function currentDay(){
 var mydate=new Date();
 var mymonth=mydate.getMonth()+1;
 var myday= mydate.getDate();
 var myyear= mydate.getYear(); 
 mymonth=mymonth<10&#63;"0"+mymonth:mymonth;
 myday=myday<10&#63;"0"+myday:myday;
 var day=myyear+"-"+mymonth+"-"+myday; 
 return day;
}