Seleciona todos os valores do CheckBox

function selectAllCheckBox( filterId) {
var check = document.getElementById("filter_" + filterId + "_all");
var select = document.getElementById("filter_" + filterId);
var options = select.options;
for(var i = 0; i < options.length; i++) {
var option = options.item(i);
option.selected = check.checked;
}
}