diff --git a/.eslintrc.json b/.eslintrc.json
index bf40dfa1..e0b14e79 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -17,6 +17,7 @@
   "rules": {
     "arrow-body-style": ["warn", "as-needed"],
     "no-empty": "off",
+    "no-undef": "off",
     "@typescript-eslint/no-empty-function": "off",
     "@typescript-eslint/prefer-for-of": "warn",
     "no-var": "warn",
diff --git a/js/locationfilter.js b/js/locationfilter.js
index d79bcd98..eed444e6 100644
--- a/js/locationfilter.js
+++ b/js/locationfilter.js
@@ -13,11 +13,10 @@
  * Version: 0.1
  */
 L.LatLngBounds.prototype.modify = function (map, amount) {
-  let sw = this.getSouthWest(),
-    ne = this.getNorthEast(),
-    swPoint = map.latLngToLayerPoint(sw),
+  const swPoint = map.latLngToLayerPoint(sw),
     nePoint = map.latLngToLayerPoint(ne);
-
+  let sw = this.getSouthWest(),
+    ne = this.getNorthEast();
   sw = map.layerPointToLatLng(
     new L.Point(swPoint.x - amount, swPoint.y + amount)
   );
@@ -108,7 +107,7 @@ L.LocationFilter = L.Control.extend({
       anchor: [-10, -10],
       size: [13, 13]
     });
-    this._moveMarker.on("drag", function (e) {
+    this._moveMarker.on("drag", (e) => {
       const markerPos = that._moveMarker.getLatLng(),
         latDelta = markerPos.lat - that._nw.lat,
         lngDelta = markerPos.lng - that._nw.lng;
@@ -152,7 +151,7 @@ L.LocationFilter = L.Control.extend({
        marker. Update filter corners and redraw the filter */
   _setupResizeMarkerTracking: function (marker, options) {
     const that = this;
-    marker.on("drag", function (e) {
+    marker.on("drag", (e) => {
       const curPosition = marker.getLatLng(),
         latMarker = options.moveAlong.lat,
         lngMarker = options.moveAlong.lng;
@@ -170,7 +169,7 @@ L.LocationFilter = L.Control.extend({
         that._swMarker.getLatLng(),
         that._seMarker.getLatLng()
       ];
-      corners.sort(function (a, b) {
+      corners.sort((a, b) => {
         if (a.lat != b.lat) return b.lat - a.lat;
         else return a.lng - b.lng;
       });
@@ -188,7 +187,7 @@ L.LocationFilter = L.Control.extend({
        given marker */
   _setupDragendListener: function (marker) {
     const that = this;
-    marker.on("dragend", function (e) {
+    marker.on("dragend", (e) => {
       // that.fire("change", {bounds: that.getBounds()});
     });
   },