JSFiddle - React, Tailwind, and code Playground

HTML

<form action="index.php" method="post">
<div id=mujdiv></div>
<p><input type="button" value="pridat" onclick="xxx()"></p>
<p><input type="submit" value="Ulozit udaje"></p>
</form>
<script>
function xxx() {
var div, str;
str = '\
<p>Meno: <input type="text" name="meno[]"></p>\
<p>Priezvisko: <input type="text" name="priez[]"></p>\
<p>Rodne cislo: <input type="text" name="rc[]"></p>\
<p>Mesto: <input type="text" name="mesto[]"></p>\
<hr>\
';
div = document.getElementById('mujdiv');
div.innerHTML += str;
}

xxx(); // aby pridal prvni formular
</script>