Edit in JSFiddle

<p>c1 <input id="c1" type="checkbox" /> / c2 <input id="c2" type="checkbox" checked /></p>
<p><button id="check">Check!</button></p>

$('#check').on('click', function(event) {
    var $c1 = $('#c1');
    var $c2 = $('#c2');
    var message =
        'c1:' +
        ' attr=' + $c1.attr('checked') +
        ' prop=' + $c1.prop('checked') +
        '\n' +
        'c2:' +
        ' attr=' + $c2.attr('checked') +
        ' prop=' + $c2.prop('checked');
    alert(message);
});