JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE HTML>
<HTML>
<HEAD>
<TITLE> lol </title>
<script type="text/javascript">
 function tretiaMocnina(vstupnecislo) {
                if (vstupnecislo == 1){

              return "co to robis";

   } else  { return Math.pow(vstupnecislo,3);
  }
}
</script>
</head>
<body>
<script>
var cislo=2;
var vysledneCislo=tretiaMocnina(cislo);
if(isNaN(vysledneCislo))
{alert ("si hlupak");}
else
{alert("Takze " + cislo + " na tretiu je " + vysledneCislo);}
</script>
</body>
</html>