jquery chek radio

1// jQuery version 1.6 or above use:  
2$("#myRadioID").prop("checked", true);
3 
4//jQuery versions below 1.6 use:
5$("#myRadioID").attr('checked', 'checked');

1$('#element').click(function() {
2   if($('#radio_button').is(':checked')) { alert("it's checked"); }
3});
4

1$(document).ready(function(){
2  $('#submit_button').click(function() {
3    if (!$("input[name='name']:checked").val()) {
4       alert('Nothing is checked!');
5        return false;
6    }
7    else {
8      alert('One of the radio buttons is checked!');
9    }
10  });
11});

1//<input type="radio" name="book_condition" value="3" >
2$("input:radio[value='3'][name='book_condition']").prop('checked',true);