JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://cdn.jsdelivr.net/foundation/4.1.2/css/foundation.min.css">
<div class="switch">
  <input id="x" name="switch-x" type="radio" checked>
  <label for="x" onclick="">Off</label>

  <input id="x1" name="switch-x" type="radio">
  <label for="x1" onclick="">On</label>

  <span></span>
</div>
      <button id="btn1">Check Selected</button>

JavaScript

$(function(){
    $("#btn1").click(function(){
        var isOn = $('#x1').is(':checked');
        alert(isOn);
    });
});