JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
 <meta http-equiv="Content-type" content="text/html; charset=iso-8859-2">
 <meta http-equiv="content-language" content="pl">
</head>
<body onLoad="window.setTimeout('getSecs()',1)">
<script>
startday = new Date();
clockStart = startday.getTime();
function initStopwatch()
{
var myTime = new Date();
       var timeNow = myTime.getTime();
       var timeDiff = timeNow - clockStart;
       this.diffSecs = timeDiff/1000;
       return(this.diffSecs);
}
function getSecs()
{
       var mySecs = initStopwatch();
       var mySecs1 = ""+mySecs;
       mySecs1= mySecs1.substring(0,mySecs1.indexOf("."));
       document.tijd.hiero.value=mySecs1
       window.setTimeout('getSecs()',1000);
       if (mySecs1==60) {alert("60 sekund ...") }
}
</script>
<form name="tijd"><input size=8 name=hiero></form>
</body>
</html>