JSFiddle - React, Tailwind, and code Playground

HTML

<input id="tussenstand"></input>
<input id="eindstand"></input>
<input id="sets"></input>
<br/>
<button id="button1" onclick="bereken();">click</button>

JavaScript

$('#button1').click(function(){
    $('#eindstand').val($('#tussenstand').val());
    $('#sets').val(Number($('#sets').val())+1);    
});