JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html 
     PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>Weird Behavior</title>
</head>
<body>
    <form action="">
        <fieldset>
            <legend>Why check is not switched?</legend>
            <input type="radio" name="myname" value="a" id="a" checked="checked"/>A
            <input type="radio" name="myname" value="b" id="b"/>B
        </fieldset>
    </form>
    <p>
      <button type="button">click me</button>
    </p>
</body>
</html>

JavaScript

$('button').click(function() {
    alert($('input[name="myname"][value="b"]').length);
    $('input[name="myname"][value="b"]').attr('checked','checked');
    $('#b').attr('checked',true);
    alert($('input[name="myname"]:checked').val());
});