JSFiddle - React, Tailwind, and code Playground

HTML

<form class="totalpayment">
    <input class="paid" type="text" name="numberOne" />
    <input class="due" type="text" name="numberTwo" />
    <button>Add</button>
</form>
<p class="total"></p>

JavaScript

// Sum the value when submitting the form
$(".totalpayment").submit(function(e){
    e.preventDefault();
    var paid = parseInt($('.paid').val());
    var due = parseInt($('.due').val());
    $(".total").html(paid + due);
});