JSFiddle - React, Tailwind, and code Playground

HTML

<div id="countdown"></div>

JavaScript

function ShowTime() {
  var now = new Date();
    if (now.getHours() > 10){
        var hrs =10-now.getHours()+24;
        if(now.getDay() == 5){
            var hrs = hrs + 48;
        }
        if(now.getDay() == 6){
            var hrs = hrs + 24;
        }
        
    }else{
  var hrs = 10-now.getHours();
         }

  var mins = 60-now.getMinutes();
  var secs = 60-now.getSeconds();

      timeLeft = "Du har nu "+hrs+' timer '+mins+' minutter '+secs+' sekunder' +" til at gennemføre en ordre - og dermed sikre dig leveringen indenfor 24 timer";
  $("#countdown").html(timeLeft);
}

var countdown;
function StopTime() {
    clearInterval(countdown);

}

setInterval(ShowTime ,1000);