JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.0/jquery.min.js"></script>
<h2>Se scrie un sir(cuvant) in ordine inversa</h2>
<input type ='text' id='src'>
<input type = "button" id='apasaBtn' value = "INVERSEAZA SIRUL">
<!-- added by lightpoint -->
<div id='rezultat'>&nbsp</div>

JavaScript

/* functia oglinda scrie un sir in ordine inversa
se foloseste un ciclu for care muta caracter cu caracter
ATENTIE - folosim concatenarea care completeaza un sir
de la dreapta la stanga
*/
function oglinda(x) {
  var oglx = "";
  for (var i = x.length - 1; i >= 0; i--) {
    oglx = oglx.concat(x[i]);
  }
  return oglx;
}
 
 //added by lightpoint
 $(document).ready(function() {
  	$("#rezultat").css({
	  	'font-size': '32px',
			'font-weight': 'bold'
		});
    
		$('#apasaBtn').click(function() {
    var value = $('#src').val();
  	$('#rezultat').html(value.length === 0 ?  "EROARE: sirul este vid!" : oglinda(value));
 	 });
 });