JSFiddle - React, Tailwind, and code Playground

HTML

<form action="index.php">
    <input type="radio" name="pagto" value="A>">
    <input type="radio" name="pagto" value="B">
    <input type="radio" name="pagto" value="C">
    <input type="radio" name="pagto" value="D">
</form>

JavaScript

var radios = document.querySelectorAll('input[type="radio"]');
[].forEach.call(radios, function (radio) {
    radio.addEventListener('change', function (e) {
        var form = (function (el) {
            while (el.tagName.toLowerCase() != 'form') el = el.parentNode;
            return el;
        })(e.target);
        form.submit();
    });
});