Source: bemap-ol/bemap-map-ol-polygon.js

/**
 * Add a bemap.Polygon to the layer
 * @public
 * @param {bemap.Polygon} bemap.Polygon.
 * @param {object} options
 * @return {bemap.OlMap}
 */
bemap.OlMap.prototype.addPolygon = function(polygon, options) {
    if (polygon && bemap.inheritsof(polygon, bemap.Polygon)) {
        polygon.native = new ol.Feature({
            geometry: new ol.geom.Polygon([polygon.getLonLatArrays()]),
        });

        if (polygon.map === null) {
            polygon.map = this;
        }

        if (polygon.id) {
            polygon.native.setId(polygon.id);
        }

        bemap.OlMap.prototype._addOwnToProperties(polygon);

        polygon.native.getGeometry().transform(bemap.Map.PROJ.EPSG_WGS84, this.native.getView().getProjection());

        if (polygon.style) {
            if (polygon.style.native === null) {
                this.buildPolygonStyle(polygon.style);
            }
            polygon.native.setStyle(polygon.style.native);
        }

        var opts = options || {};
        var l = null;

        if (opts.layer && bemap.inheritsof(opts.layer, bemap.VectorLayer)) {
            l = opts.layer;
        } else {
            l = this.getLayerByName(bemap.Map.DEFAULT_LAYER.POLYGON);
            if (l === null) {
                l = new bemap.VectorLayer({
                    name: bemap.Map.DEFAULT_LAYER.POLYGON
                });
                this.addLayer(l);
            }
        }

        if (polygon.layer === null) {
            polygon.layer = l;
        }

        l.native.getSource().addFeature(polygon.native);
    }
    return this;
};

/**
 * Remove a polygon from his layer.
 * @public
 * @param {bemap.Polygon} polygon the polygon object to remove.
 */
bemap.OlMap.prototype.removePolygon = function(polygon) {
    if (polygon && polygon.layer && polygon.layer.native && bemap.inheritsof(polygon, bemap.Polygon)) {
        polygon.layer.native.getSource().removeFeature(polygon.native);
        polygon.layer = null;
        polygon.map = null;
    }
    return this;
};

/**
 * Set the listner when an specified eventType occur on bemap.Polygon.
 * @public
 * @param {bemap.Polygon} polygon
 * @param {bemap.Map.EventType} eventType Event type.
 * @param {function} callback Function will be called when the specified eventType is occur.
 * @param {object} options options.
 * @return {bemap.Listener} this.
 */
bemap.OlMap.prototype.onPolygon = function(polygon, eventType, callback, options) {
    return this._onFeature(polygon, eventType, callback, options, {
        singleFeature: true
    });
};

/**
 * Set the listner when an specified eventType occur on all bemap.Polygon.
 * @public
 * @param {bemap.Map.EventType} eventType Event type.
 * @param {function} callback Function will be called when the specified eventType is occur.
 * @param {object} options options.
 * @return {bemap.Listener} this.
 */
bemap.OlMap.prototype.onPolygons = function(eventType, callback, options) {
    return this._onFeature(null, eventType, callback, options, {
        polygons: true
    });
};

/**
 * Define the draggable capability for bemap.Polygon.
 * @protected
 * @param {bemap.Polygon} polygon bemap object.
 * @param {function} callback Function will be called when the specified eventType is occur.
 * @param {object} options Options.
 * @param {bemap.Layer} options.layerFilter set the bemap layer used as filter.
 * @return {bemap.Listener} bemap.listener.
 */
bemap.OlMap.prototype.draggablePolygon = function(polygon, callback, options) {
    return this._draggableFeature(polygon, callback, options, {
        singleFeature: true
    });
};

/**
 * Define the draggable capability for all bemap.Polygon.
 * @protected
 * @param {function} callback Function will be called when the specified eventType is occur.
 * @param {object} options Options.
 * @param {bemap.Layer} options.layerFilter set the bemap layer used as filter.
 * @return {bemap.Listener} bemap.listener.
 */
bemap.OlMap.prototype.draggablePolygons = function(callback, options) {
    return this._draggableFeature(null, callback, options, {
        polygons: true
    });
};

/**
 * Update the coordinates from the native map browser.
 * @public
 */
bemap.OlMap.prototype.updatePolygonCoordinates = function(polygon) {
  var pol = polygon.native.getGeometry().getCoordinates(true)[0];

  for (var i = 0; i < pol.length; i++) {
    var polc = ol.proj.transform(pol[i], this.native.getView().getProjection(), bemap.Map.PROJ.EPSG_WGS84);
    var coord = polygon.coords[i];

    if(coord && coord !== null && bemap.inheritsof(coord, bemap.Coordinate)) {
      coord.setLon(polc[0]);
      coord.setLat(polc[1]);
    } else {
      polygon.coords[i] = new bemap.Coordinate(polc[0], polc[1]);
   }
  }

  if(polygon.coords.length > pol.length) {
    for (var j = pol.length; j < polygon.coords.length; j++) {
      polygon.coords.pop();
    }
  }
};