JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button" onclick="tabelica()">Klikni</button>
<div id="mojdiv"></div>

CSS

td {
  border: 1px solid white;
  width: 20px;
  height: 20px;
}

.mojclass {
  background-color: green;
}

JavaScript

function tabelica() {
  var stevilo = prompt("Vstavi") * 1;
  var mojdiv = document.getElementById("mojdiv");
  var tabela = document.createElement("TABLE");
  mojdiv.appendChild(tabela);
  var vrstica = document.createElement("TR");
  tabela.appendChild(vrstica);

  for (var j = 0; j < stevilo; j++) {
    var celica = document.createElement("TD");
    vrstica.appendChild(celica);
    celica.className = "mojclass";
  }
}