How can I check whether a radio button is selected with JavaScript?

Question

I have two radio buttons within an HTML form. A dialog box appears when one of the fields is null. How can I check whether a radio button is selected?

Answer 1

I just want to ensure something gets selected (using jQuery):

// html
 Male  Female

// gender (required)
var gender_check = $('input:radio[name=gender]:checked').val();
if ( !gender_check ) {
    alert("Please select your gender.");
    return false;
}