fixed issue 6508 of plotly.js.

fix lint.

Author: nickmelnikov82

src/traces/scattermapbox/plot.js

@@ -57,7 +57,7 @@ proto.addSource = function(k, opts, cluster) {
         });
     }
     var isSourceExists = this.subplot.map.getSource(this.sourceIds[k]);
-    if (!!isSourceExists) {
+    if(isSourceExists) {
         isSourceExists.setData(opts.geojson);
     } else {
         this.subplot.map.addSource(this.sourceIds[k], sourceOpts);
@@ -84,8 +84,8 @@ proto.addLayer = function(k, opts, below) {
     var layerId = this.layerIds[k];
     var layerExist = this.subplot.getMapLayers().filter(function(mbLayer) {
         return mbLayer.id === layerId;
-    })
-    if (layerExist.length) {
+    });
+    if(layerExist.length) {
         this.subplot.map.removeLayer(layerId);
     }
     this.subplot.addLayer(source, below);