Extend L.GeoJson to allow changes to the Feature Group after creation. Useful for dynamic filtering and map layer event processing.

leaflet-geojson-setoptions.js

L.GeoJSON.include({
  setOptions: function(opts) {
    //save original json data
    this._data = this._data || this.toGeoJSON();

    //destory layer group
    this.clearLayers();
    L.setOptions(this, opts);

    //recreate layer group
    this.addData(this._data);
  }
});

Usage example:

geojson.setOptions({
  filter: function (feature, layer) {
    return feature.properties.category == selectedCat;
  }
});