How can we access the value of a radio button using the DOM?

Question

How can we access the value of a radio button using the DOM?

For eg. we have the radio button as :

Answer 1

Just to "generify" Canavar's very helpful function:

function getRadioValue(theRadioGroup)
{
    var elements = document.getElementsByName(theRadioGroup);
    for (var i = 0, l = elements.length; i < l; i++)
    {
        if (elements[i].checked)
        {
            return elements[i].value;
        }
    }
}

... which would now be referenced thusly:

getRadioValue('sex');

Strange that something like this isn't already a part of prototype.js.