问如何在control.layers中获取所选层？

EN

// Add method to layer control class
L.Control.Layers.include({
    getActiveOverlays: function () {

        // Create array for holding active layers
        var active = [];

        // Iterate all layers in control
        this._layers.forEach(function (obj) {

            // Check if it's an overlay and added to the map
            if (obj.overlay && this._map.hasLayer(obj.layer)) {

                // Push layer to active array
                active.push(obj.layer);
            }
        });

        // Return array
        return active;
    }
});

var control = new L.Control.Layers(...),
    active = control.getActiveOverlays();