JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <input type="text" value="asd" id="uchwyt2" name="ile">
<form>
<input type="checkbox" value="ilosc" name="productsIds" />
<input type="text" name="wystawionailosc" value="wystawionailosc" id="uchwyt" />
</form>
</div>

JavaScript

var field = document.getElementById('uchwyt');

field.addEventListener('change',function(e){
        var field2 = document.getElementById('uchwyt2');
        field2.value = field.value;
});