gistfile1.js

Template.facetFilterItem.helpers({
  isChecked: function(name, _id) {
    return _.indexOf(Facet.get(name), _id) !== -1;
  }
});

Facet = (function() {
  var set = function(name, value) {
    var current = Router.current();
    var params = {};
    var query;
    params[name] = value;

    if (! params[name].length)
      query = _.omit(current.queryParams, name);
    else
      query = _.extend(current.queryParams, params);
    
    Router.go(current.route.name, current.params, { query: query });
  };
  var get = function(name) {
    var current = Router.current().params[name];
    if (! current)
      return [];
    if (! _.isArray(current))
      current = [current];

    return current;
  };

  return {
    add: function(name, value) {
      var params = get(name) || [];

      if (_.indexOf(params, value) === -1)
        params.push(value);

      set(name, params);
    },

    remove: function(name, value) {
      set(name, _.without(get(name), value));
    },

    get: function(name) {
      return get(name);
    }
  };
})();

Template.facetFilter.events({
  'click input[type=checkbox]': function(event, template) {
    var name = event.target.name;
    var value = event.target.value;

    if ($(event.target).is(':checked'))
      Facet.add(name, value);
    else
      Facet.remove(name, value);
  }
});