退職日まで日数を求める・JSでカウントダウンコードを構築してみた😆

var showDiffDate = function( tYear, tMonth, tDay) {
    var nowDate = new Date();
    var dnumNow = nowDate.getTime();
    var targetDate = new Date( tYear, tMonth-1, tDay );
    var dnumTarget = targetDate.getTime();

    var diffMSec = dnumTarget - dnumNow;
    var diffDays = diffMSec / ( 1000 * 60 * 60 * 24 );
    var showDays = Math.ceil( diffDays ); 
    var Msg;
    if( showDays >= 0 ) {
       Msg = "" + showDays + " days(" + function(){
         var is_days = parseInt(parseInt(showDays) - Math.floor(showDays / 7) * 2);
         is_days = (nowDate.getDay() === 0)?is_days -2:is_days;
         is_days = (nowDate.getDay() === 6)?is_days -3:is_days;
         return is_days;
       }() +")";
    }
    else {
       Msg = "" + (showDays * -1) + "";
    }
    return Msg;
 };

 document.getElementById("days").innerText = showDiffDate(2022,7,15);