Best way to get true/false from a checkbox?

Best way to get true/false from a checkbox?

Hi.
 
I just started to use jquery.
 
What is the easy way to do this:
 
  1.         var AllDay = null;
            function GetCheckBoxValue() {
                if ($('#myCheckBox).attr('checked') == false) {
                       AllDay = "false";
                } else {
                        AllDay = "true";
                }
            }






I need to get the true or false from the checkbox. Above works fine, but there most be a smarter way to do it.