JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test1">
    <input type="radio" name="test1" checked="checked" />
</div>

<input type="radio" name="test2" checked="checked" />

<form>
    <input type="radio" name="test3" checked="checked" />
</form>

<input type="radio" id="test4" name="test4" checked="checked" />

JavaScript

// in webkit orignal radio is

// not checked
$( '#test1' ).clone();

// not checked
$( '<input type="radio" name="test2" checked="checked" />' );

// checked
$( '<input type="radio" name="test3" checked="checked" />' );

// not checked in old webkit
$( "#test4" ).clone();

// same thing would happen even if jQuery.support.checkClone = false

// not checked in old webkit too, but can be fixed if jQuery.support.checkClone = false
jQuery("form").append( '<input name="test5" type="radio" checked="checked" />' );

// in all other browsers original and append radio will be checked