JSFiddle - React, Tailwind, and code Playground

HTML

<div id="main"></div>
<input type="text" id="tst"><input type="button" id="kn" value="klikk">

JavaScript

$('#kn').click(function(){

$('#main').html(parseFloat('10,5')*$('#tst').val);

console.log(parseInt($('#tst').val));

});