JSFiddle - React, Tailwind, and code Playground
by gentou
HTML
1 EURO =
<input name="Kurs" type="text" size="4" id="course">PLN
<div id="board"></div>
<form>
Nazwa transakcji:<br>
<input type="text" name="firstname"><br>
Ilosc:<br>
<input type="text" name="lastname">
</form>
JavaScript
var ratio = document.getElementById("course");
var board = document.getElementById("board");
ratio.addEventListener("change", function(){
board.innerHTML = ratio.value;
});