JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="clock" />

JavaScript

setInterval(clock, 1000);

function clock() {
   var date = new Date();
   var h = date.getHours();   if(h<10) h = "0"+h;
   var m = date.getMinutes(); if(m<10) m = "0"+m;
   var s = date.getSeconds(); if(s<10) s = "0"+s;
    var clockElement = document.getElementById("clock");
    clockElement.value = h + ":" + m  + ":" + s;
}