how to check html radio button is checked code example

Example 1: check if radio button is checked

$('#element').click(function() {
   if($('#radio_button').is(':checked')) { alert("it's checked"); }
});

Example 2: checkbox as radio button

input[type=checkbox]:not(old) + label,
input[type=radio   ]:not(old) + label{
  display      : inline-block;
  margin-left  : -2em;
  line-height  : 4em;
}