[Use this][1] to determine if the checkbox is checked and store it in a variable as a bool value.


  [1]: http://jquery-howto.blogspot.in/2013/02/jquery-test-check-if-checkbox-checked.html


After that for postBody you could use:

    "mypostdata="+$('my_value').value +"&isChecked="+isChecked;

Where isChecked is the js variable you stored the bool value in and it will be passed to the post param: isChecked