判断日期之差

function checkTime(){
    var dateInp=$("#dateInp").val();
    var day1=Date.parse(dateInp.replace(/-/g, "/"));
    var nowDate = new Date();
    var dateStr = nowDate.getFullYear()+"/"+(nowDate.getMonth() + 1)+"/"+nowDate.getDate();                
    var day2=Date.parse(dateStr);
    var apartTime=day1-day2;
    var apartDay=parseInt(apartTime / (1000 * 60 * 60 * 24));
    if(apartDay ==0){
        alert("不能预约当天");
        return false;
    }else if (apartDay < 1 || apartDay > 3){
        alert("预约日期超出范围");
        return false;
    }  
}