JSFiddle - React, Tailwind, and code Playground

HTML

<form name="form">
    <input type="radio" name="foo"> Foo1<br/>
    <input type="radio" name="foo"> Foo2<br/>
    <input type="button" name="validateFoo" value="Validate Foo"/><br/>
    <br/>
    <input type="radio" name="bar"> Bar1<br/>
    <input type="radio" name="bar"> Bar2<br/>
    <input type="button" name="validateBar" value="Validate Bar"/><br/>
</form>

JavaScript

var validateRadioSelected = function(name) {
    var rs = document.form[name], i;
    for (i=0; i<rs.length; i++) {
        if (rs[i].checked) {
            return true;
        }
    }
    return false;
};

document.form.validateFoo.onclick = function() {
    alert("Foo valid? - " + validateRadioSelected('foo'));
};

document.form.validateBar.onclick = function() {
    alert("Bar valid? - " + validateRadioSelected('bar'));
};