Use blocked scoped variables

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

src/ol/featureloader.js

@@ -26,10 +26,10 @@ export function loadFeaturesXhr(url, format, success, failure) {
      * @this {ol.source.Vector|ol.VectorTile}
      */
     function(extent, resolution, projection) {
-      var xhr = new XMLHttpRequest();
+      const xhr = new XMLHttpRequest();
       xhr.open('GET',
-          typeof url === 'function' ? url(extent, resolution, projection) : url,
-          true);
+        typeof url === 'function' ? url(extent, resolution, projection) : url,
+        true);
       if (format.getType() == FormatType.ARRAY_BUFFER) {
         xhr.responseType = 'arraybuffer';
       }
@@ -40,9 +40,9 @@ export function loadFeaturesXhr(url, format, success, failure) {
       xhr.onload = function(event) {
         // status will be 0 for file:// urls
         if (!xhr.status || xhr.status >= 200 && xhr.status < 300) {
-          var type = format.getType();
+          const type = format.getType();
           /** @type {Document|Node|Object|string|undefined} */
-          var source;
+          let source;
           if (type == FormatType.JSON || type == FormatType.TEXT) {
             source = xhr.responseText;
           } else if (type == FormatType.XML) {
@@ -55,7 +55,7 @@ export function loadFeaturesXhr(url, format, success, failure) {
           }
           if (source) {
             success.call(this, format.readFeatures(source,
-                {featureProjection: projection}),
+              {featureProjection: projection}),
             format.readProjection(source), format.getLastExtent());
           } else {
             failure.call(this);
@@ -87,12 +87,12 @@ export function loadFeaturesXhr(url, format, success, failure) {
  */
 export function xhr(url, format) {
   return loadFeaturesXhr(url, format,
-      /**
+    /**
        * @param {Array.<ol.Feature>} features The loaded features.
        * @param {ol.proj.Projection} dataProjection Data projection.
        * @this {ol.source.Vector}
        */
-      function(features, dataProjection) {
-        this.addFeatures(features);
-      }, /* FIXME handle error */ nullFunction);
+    function(features, dataProjection) {
+      this.addFeatures(features);
+    }, /* FIXME handle error */ nullFunction);
 }