Use blocked scoped variables

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

examples/earthquake-clusters.js

@@ -17,21 +17,21 @@ import Style from '../src/ol/style/Style.js';
 import Text from '../src/ol/style/Text.js';
 
 
-var earthquakeFill = new Fill({
+const earthquakeFill = new Fill({
   color: 'rgba(255, 153, 0, 0.8)'
 });
-var earthquakeStroke = new Stroke({
+const earthquakeStroke = new Stroke({
   color: 'rgba(255, 204, 0, 0.2)',
   width: 1
 });
-var textFill = new Fill({
+const textFill = new Fill({
   color: '#fff'
 });
-var textStroke = new Stroke({
+const textStroke = new Stroke({
   color: 'rgba(0, 0, 0, 0.6)',
   width: 3
 });
-var invisibleFill = new Fill({
+const invisibleFill = new Fill({
   color: 'rgba(255, 255, 255, 0.01)'
 });
 
@@ -39,9 +39,9 @@ function createEarthquakeStyle(feature) {
   // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
   // standards-violating <magnitude> tag in each Placemark.  We extract it
   // from the Placemark's name instead.
-  var name = feature.get('name');
-  var magnitude = parseFloat(name.substr(2));
-  var radius = 5 + 20 * (magnitude - 5);
+  const name = feature.get('name');
+  const magnitude = parseFloat(name.substr(2));
+  const radius = 5 + 20 * (magnitude - 5);
 
   return new Style({
     geometry: feature.getGeometry(),
@@ -56,16 +56,17 @@ function createEarthquakeStyle(feature) {
   });
 }
 
-var maxFeatureCount, vector;
-function calculateClusterInfo(resolution) {
+let maxFeatureCount;
+let vector = null;
+const calculateClusterInfo = function(resolution) {
   maxFeatureCount = 0;
-  var features = vector.getSource().getFeatures();
-  var feature, radius;
-  for (var i = features.length - 1; i >= 0; --i) {
+  const features = vector.getSource().getFeatures();
+  let feature, radius;
+  for (let i = features.length - 1; i >= 0; --i) {
     feature = features[i];
-    var originalFeatures = feature.get('features');
-    var extent = _ol_extent_.createEmpty();
-    var j, jj;
+    const originalFeatures = feature.get('features');
+    const extent = _ol_extent_.createEmpty();
+    let j, jj;
     for (j = 0, jj = originalFeatures.length; j < jj; ++j) {
       _ol_extent_.extend(extent, originalFeatures[j].getGeometry().getExtent());
     }
@@ -74,16 +75,16 @@ function calculateClusterInfo(resolution) {
         resolution;
     feature.set('radius', radius);
   }
-}
+};
 
-var currentResolution;
+let currentResolution;
 function styleFunction(feature, resolution) {
   if (resolution != currentResolution) {
     calculateClusterInfo(resolution);
     currentResolution = resolution;
   }
-  var style;
-  var size = feature.get('features').length;
+  let style;
+  const size = feature.get('features').length;
   if (size > 1) {
     style = new Style({
       image: new CircleStyle({
@@ -99,22 +100,22 @@ function styleFunction(feature, resolution) {
       })
     });
   } else {
-    var originalFeature = feature.get('features')[0];
+    const originalFeature = feature.get('features')[0];
     style = createEarthquakeStyle(originalFeature);
   }
   return style;
 }
 
 function selectStyleFunction(feature) {
-  var styles = [new Style({
+  const styles = [new Style({
     image: new CircleStyle({
       radius: feature.get('radius'),
       fill: invisibleFill
     })
   })];
-  var originalFeatures = feature.get('features');
-  var originalFeature;
-  for (var i = originalFeatures.length - 1; i >= 0; --i) {
+  const originalFeatures = feature.get('features');
+  let originalFeature;
+  for (let i = originalFeatures.length - 1; i >= 0; --i) {
     originalFeature = originalFeatures[i];
     styles.push(createEarthquakeStyle(originalFeature));
   }
@@ -134,13 +135,13 @@ vector = new VectorLayer({
   style: styleFunction
 });
 
-var raster = new TileLayer({
+const raster = new TileLayer({
   source: new Stamen({
     layer: 'toner'
   })
 });
 
-var map = new Map({
+const map = new Map({
   layers: [raster, vector],
   interactions: defaultInteractions().extend([new Select({
     condition: function(evt) {