JSFiddle - React, Tailwind, and code Playground

HTML

<fieldset id="fs1" name="clubfields" disabled>
 <legend> <label>
  <input type=checkbox name=club onchange="form.clubfields.disabled = !checked">
  Use Club Card
 </label> </legend>
 <p><label>Name on card: <input name=clubname required></label></p>
 <p><label>Card number: <input name=clubnum required pattern="[-0-9]+"></label></p>
 <p><label>Expiry date: <input name=clubexp type=month></label></p>
</fieldset>
<div id="message"></div>

JavaScript

var fs1 = document.getElementById("fs1");
var message = document.getElementById("message");
function log(m) { message.innerHTML += m + "<br>"; }
log("fs1.name=" + fs1.name);
log("fs1.disabled=" + fs1.disabled);
log("fs1.elements=" + fs1.elements);
log("fs1.type=" + fs1.type);