JSFiddle - React, Tailwind, and code Playground

by bluey

HTML

<span id='thisid' data-discount_tendered='0.00'></span>
<span id='value'>1.10</span>
<button id='btn'>Go</button>

JavaScript

$("#btn").click( function() {
    discount = $("#thisid").data("discount_tendered");
    // alert(discount);
    value = $("#value").text();
    valueDec = parseFloat(value);
    // alert(value);
    newDiscountVal = discount += valueDec;
    // alert(newDiscountVal);
    $("#thisid").attr("data-discount_tendered", newDiscountVal);
});