leaflet_markercluster.drupal.js refactoring (also 'Issue #3257616: Group of...

(function ($) {

  Drupal.Leaflet.prototype.add_features = function (mapid, features, initial) {

    const leaflet_markercluster_options = this.settings.leaflet_markercluster.options && this.settings.leaflet_markercluster.options.length > 0 ? JSON.parse(this.settings.leaflet_markercluster.options) : {};

    const leaflet_markercluster_inlcude_path = this.settings.leaflet_markercluster.include_path;

    var leaflet_markercluster_options = this.settings.leaflet_markercluster.options && this.settings.leaflet_markercluster.options.length > 0 ? JSON.parse(this.settings.leaflet_markercluster.options) : {};

    var leaflet_markercluster_inlcude_path = this.settings.leaflet_markercluster.include_path;

    var cluster_layer = new L.MarkerClusterGroup(leaflet_markercluster_options);

    var collections_cluster_layers = {};

    for (var i = 0; i < features.length; i++) {

      var feature = features[i];

      var lFeature;

    const cluster_layer = new L.MarkerClusterGroup(leaflet_markercluster_options);

    for (let i = 0; i < features.length; i++) {

      let feature = features[i];

      let lFeature;

      // dealing with a layer group

      if (feature.group) {

        var lGroup = this.create_feature_group(feature);

        for (var groupKey in feature.features) {

          var groupFeature = feature.features[groupKey];

          let groupFeature = feature.features[groupKey];

          lFeature = this.create_feature(groupFeature);

          if (lFeature !== undefined) {

            if (lFeature.setStyle) {

          }

        }

        // @todo we need to correctly handle the groups here

        cluster_layer.addLayer(lGroup);

        // Correctly handle the groups here

        this.add_overlay(feature.label, lGroup, false, mapid);

      }

      else {

        lFeature = this.create_feature(feature);