Multiple checkbox filter with jquery

I am working with jquery input checkbox filter. While I am searching for the reference I got the following code from 'StackOverflow' that works perfectly. But my problem is how to use this code with logical and operation. ie, if I checked two checkboxes, it only displays content with both value, not either or

$(document).ready(function () {
$('.post').show();

$('.menu-item').find('input:checkbox').on('click', function () {
    var post = $('.post').hide();

    var elements = $('.menu-item').find('input:checked');

    if(elements.length){
        elements.each(function () {
            post.filter('.' + this.id).show();
        });
    }
    else
        post.show();
  });
}); 

http://jsfiddle.net/mzvNL/1/