if ($('#check_id').is(":checked"))
{
// it is checked
}
$('#checkbox_id:checked').val();
//if checkbox is selected than gets its value
$("input[type='checkbox']").val();
$('#check_id').val();
$(":checkbox[value=4]").prop("checked","true");
$.each(arrayValues, function(i, val){
$("input[value='" + val + "']").prop('checked', true);
});
$('.myCheckbox')[0].checked = true;
$('.myCheckbox')[0].checked = false;
$('#chkbox').click();
var grenval = $('.green').val();
$('.showCheckedValue').text(redval+'&'+grenval );