JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" value="add 80 and prompt hidden total" id="next" />
<input type="hidden" value="0" id="start" />

JavaScript

$("#next").click(function() {
    var startElement = $("#start");
    var value = parseInt(startElement.val());
    startElement.val(value + 80);
    alert(startElement.val());
});