JSFiddle - React, Tailwind, and code Playground

HTML

<table id="user123">
<tr>
<td><input name="r520" value="G" type="radio"></td>
<td><input name="r520" value="A" type="radio"></td>
<td><input name="r520" value="X" type="radio"></td>
<td><input name="r520" value="" type="radio" checked></td>
<td>2011-06-01</td>
</tr>
<tr>
<td><input name="r767" value="G" type="radio"></td>
<td><input name="r767" value="A" type="radio"></td>
<td><input name="r767" value="X" type="radio"></td>
<td><input name="r767" value="" type="radio"></td>
<td>2011-06-03</td>
</tr>
</table>

JavaScript

$("#user123 tr").each(function() {
    if($(":radio:checked", this).length == 0) {
        $(":radio[value=A]", this).attr("checked", true);        
    }
});