$('input[filterItem]').each(function() 
                { 
                    $(this).prop("checked", isChecked);
                });

@Html.CheckBoxFor(model => Model.Filter.TimeOff, new { @onclick = "filterChanged(this.checked, 'TimeOff');", @filterItem = "yes" })

@Html.CheckBoxFor(model => Model.Filter.TimeOff, new { @class="flat-red",  @onclick = "filterChanged(this.checked, 'TimeOff');", @filterItem = "yes" })