JSFiddle - React, Tailwind, and code Playground

HTML

<p>Select "fiat", and see magic happen</p>

<form action="" id="cars">
    <select name="cars" id="car_selector">
        <option value="volvo">Volvo</option>
        <option value="saab">Saab</option>
        <option value="fiat">Fiat</option>
        <option value="audi">Audi</option>
    </select>
    <p>&nbsp;</p>
    <label class="hidden_option">Why would you DO that?</label>
    <input type="text" name="reason" class="hidden_option" />
</form>

CSS

.hidden_option{
 display: none;   
}

JavaScript

$(function() {
  enable_cb();
  $("#group1").click(enable_cb);
});

function enable_cb() {
  if (this.checked) {
    $("input.group1").removeAttr("disabled");
  } else {
    $("input.group1").attr("disabled", true);
  }
}