Leaflet自定义字段聚类实现与扩展

/**
 * 按字段聚合
 */
var DistrictClusterGroup = L.DistrictClusterGroup = L.FeatureGroup.extend({
  options: { disableClusteringAtZoom: 7, _maxZoom: 12, areaInfo: [], maxCount: 17, clusterField: "county" },
   clusterMaxZoom:15,
   clusterMinZoom:11,
  initialize: function (options) {
  
    this.options.areaInfo=[{adcd:"330702000000000",county:"婺城区",lng:119.5729412,lat:29.08920379},
    {adcd:"330703000000000",county:"金东区",lng:119.6840323,lat:29.10222513},
    {adcd:"330723000000000",county:"武义县",lng:119.8074529,lat:28.89903799},
    {adcd:"330726000000000",county:"浦江县",lng:119.8816691,lat:29.45555857},
    {adcd:"330727000000000",county:"磐安县",lng:120.4408777,lat:29.05704572},
    {adcd:"330781000000000",county:"兰溪市",lng:119.4540353,lat:29.21184071},
    {adcd:"330782000000000",county:"义乌市",lng:120.07279,lat:29.30560302},
    {adcd:"330783000000000",county:"东阳市",lng:120.2389511,lat:29.29260808},
    {adcd:"330784000000000",county:"永康市",lng:120.0430468,lat:28.89360874},
    {adcd:"330785000000000",county:"金华市开发区",lng:119.5851517,lat:29.04201508}];
      if (!options._maxZoom) {
          options._maxZoom = this.options._maxZoom;
        this.clusterMaxZoom=options._maxZoom+3;
      }
      if (!options.disableClusteringAtZoom) {
          options.disableClusteringAtZoom = this.options.disableClusteringAtZoom;

      }
      if (!options.maxCount) {
          options.maxCount = this.options.maxCount;

        
      }
      if (!options.clusterField) {
          options.clusterField = this.options.clusterField;
      }
      L.Util.setOptions(this, options);
      this.groupArr = [];
  },
  //setMaxCount: function (count) {
  //    this.options.maxCount = count;
  //},
  groupArr: [],
  clusterMarkerGroup:null,
  _zoomEnd: function () {
      if (!this._map) { //May have been removed from the map by a zoomEnd handler
          return;
      }


      this._updateArea();

  },


  addLayer: function (layer) {

      //if (L.FeatureGroup.prototype.hasLayer(layer)) {
      //    return this;
      //}
      //var id = L.FeatureGroup.prototype.getLayerId(layer);