Use blocked scoped variables

In addition to using const and let, this also upgrades our linter config and removes lint (mostly whitespace).

examples/vector-layer.js

@@ -9,7 +9,7 @@ import Style from '../src/ol/style/Style.js';
 import Text from '../src/ol/style/Text.js';
 
 
-var style = new Style({
+const style = new Style({
   fill: new Fill({
     color: 'rgba(255, 255, 255, 0.6)'
   }),
@@ -29,7 +29,7 @@ var style = new Style({
   })
 });
 
-var vectorLayer = new VectorLayer({
+const vectorLayer = new VectorLayer({
   source: new VectorSource({
     url: 'data/geojson/countries.geojson',
     format: new GeoJSON()
@@ -40,7 +40,7 @@ var vectorLayer = new VectorLayer({
   }
 });
 
-var map = new Map({
+const map = new Map({
   layers: [vectorLayer],
   target: 'map',
   view: new View({
@@ -49,7 +49,7 @@ var map = new Map({
   })
 });
 
-var highlightStyle = new Style({
+const highlightStyle = new Style({
   stroke: new Stroke({
     color: '#f00',
     width: 1
@@ -69,7 +69,7 @@ var highlightStyle = new Style({
   })
 });
 
-var featureOverlay = new VectorLayer({
+const featureOverlay = new VectorLayer({
   source: new VectorSource(),
   map: map,
   style: function(feature) {
@@ -78,14 +78,14 @@ var featureOverlay = new VectorLayer({
   }
 });
 
-var highlight;
-var displayFeatureInfo = function(pixel) {
+let highlight;
+const displayFeatureInfo = function(pixel) {
 
-  var feature = map.forEachFeatureAtPixel(pixel, function(feature) {
+  const feature = map.forEachFeatureAtPixel(pixel, function(feature) {
     return feature;
   });
 
-  var info = document.getElementById('info');
+  const info = document.getElementById('info');
   if (feature) {
     info.innerHTML = feature.getId() + ': ' + feature.get('name');
   } else {
@@ -108,7 +108,7 @@ map.on('pointermove', function(evt) {
   if (evt.dragging) {
     return;
   }
-  var pixel = map.getEventPixel(evt.originalEvent);
+  const pixel = map.getEventPixel(evt.originalEvent);
   displayFeatureInfo(pixel);
 });