diff --git a/src/ol/format/GML2.js b/src/ol/format/GML2.js
index 5f6355cc68..64ac17bde4 100644
--- a/src/ol/format/GML2.js
+++ b/src/ol/format/GML2.js
@@ -13,7 +13,7 @@ import {createElementNS, getAllTextContent, makeArrayPusher, makeChildAppender,
   makeReplacer, makeSimpleNodeFactory, OBJECT_PROPERTY_NODE_FACTORY, pushParseAndPop, pushSerializeAndPop} from '../xml.js';
 
 
-  /**
+/**
  * @const
  * @type {string}
  */
@@ -69,13 +69,12 @@ GML2.prototype.readFlatCoordinates_ = function(node, objectStack) {
     }
   }
   const coordsGroups = s.trim().split(/\s+/);
-  let x, y, z;
   const flatCoordinates = [];
   for (let i = 0, ii = coordsGroups.length; i < ii; i++) {
     const coords = coordsGroups[i].split(/,+/);
-    x = parseFloat(coords[0]);
-    y = parseFloat(coords[1]);
-    z = (coords.length === 3) ? parseFloat(coords[2]) : 0;
+    const x = parseFloat(coords[0]);
+    const y = parseFloat(coords[1]);
+    const z = (coords.length === 3) ? parseFloat(coords[2]) : 0;
     if (axisOrientation.substr(0, 2) === 'en') {
       flatCoordinates.push(x, y, z);
     } else {
@@ -333,9 +332,8 @@ GML2.prototype.writeCoordinates_ = function(node, value, objectStack) {
   const points = value.getCoordinates();
   const len = points.length;
   const parts = new Array(len);
-  let point;
   for (let i = 0; i < len; ++i) {
-    point = points[i];
+    const point = points[i];
     parts[i] = this.getCoords_(point, srsName, hasZ);
   }
   writeStringTextNode(node, parts.join(' '));
@@ -349,8 +347,7 @@ GML2.prototype.writeCoordinates_ = function(node, value, objectStack) {
  * @private
  */
 GML2.prototype.writeCurveSegments_ = function(node, line, objectStack) {
-  const child = createElementNS(node.namespaceURI,
-    'LineStringSegment');
+  const child = createElementNS(node.namespaceURI, 'LineStringSegment');
   node.appendChild(child);
   this.writeCurveOrLineString_(child, line, objectStack);
 };
diff --git a/src/ol/format/GMLBase.js b/src/ol/format/GMLBase.js
index 852e1e8e43..1ebd849982 100644
--- a/src/ol/format/GMLBase.js
+++ b/src/ol/format/GMLBase.js
@@ -122,12 +122,11 @@ GMLBase.prototype.readFeaturesInternal = function(node, objectStack) {
     const context = objectStack[0];
     let featureType = context['featureType'];
     let featureNS = context['featureNS'];
-    let i, ii;
     const prefix = 'p';
     const defaultPrefix = 'p0';
     if (!featureType && node.childNodes) {
       featureType = [], featureNS = {};
-      for (i = 0, ii = node.childNodes.length; i < ii; ++i) {
+      for (let i = 0, ii = node.childNodes.length; i < ii; ++i) {
         const child = node.childNodes[i];
         if (child.nodeType === 1) {
           const ft = child.nodeName.split(':').pop();
@@ -165,7 +164,7 @@ GMLBase.prototype.readFeaturesInternal = function(node, objectStack) {
     const featureTypes = Array.isArray(featureType) ? featureType : [featureType];
     for (const p in featureNS) {
       const parsers = {};
-      for (i = 0, ii = featureTypes.length; i < ii; ++i) {
+      for (let i = 0, ii = featureTypes.length; i < ii; ++i) {
         const featurePrefix = featureTypes[i].indexOf(':') === -1 ?
           defaultPrefix : featureTypes[i].split(':')[0];
         if (featurePrefix === p) {
diff --git a/src/ol/format/GPX.js b/src/ol/format/GPX.js
index c5284c6f24..23e670a1a5 100644
--- a/src/ol/format/GPX.js
+++ b/src/ol/format/GPX.js
@@ -427,8 +427,7 @@ function applyLayoutOptions(layoutOptions, flatCoordinates, ends) {
     stride = 3;
   }
   if (stride !== 4) {
-    let i, ii;
-    for (i = 0, ii = flatCoordinates.length / 4; i < ii; i++) {
+    for (let i = 0, ii = flatCoordinates.length / 4; i < ii; i++) {
       flatCoordinates[i * stride] = flatCoordinates[i * 4];
       flatCoordinates[i * stride + 1] = flatCoordinates[i * 4 + 1];
       if (layoutOptions.hasZ) {
@@ -440,7 +439,7 @@ function applyLayoutOptions(layoutOptions, flatCoordinates, ends) {
     }
     flatCoordinates.length = flatCoordinates.length / 4 * stride;
     if (ends) {
-      for (i = 0, ii = ends.length; i < ii; i++) {
+      for (let i = 0, ii = ends.length; i < ii; i++) {
         ends[i] = ends[i] / 4 * stride;
       }
     }
diff --git a/src/ol/format/KML.js b/src/ol/format/KML.js
index 213415bb74..052ae49ca6 100644
--- a/src/ol/format/KML.js
+++ b/src/ol/format/KML.js
@@ -928,9 +928,7 @@ function readGxTrack(node, objectStack) {
   }
   const flatCoordinates = gxTrackObject.flatCoordinates;
   const whens = gxTrackObject.whens;
-  let i, ii;
-  for (i = 0, ii = Math.min(flatCoordinates.length, whens.length); i < ii;
-    ++i) {
+  for (let i = 0, ii = Math.min(flatCoordinates.length, whens.length); i < ii; ++i) {
     flatCoordinates[4 * i + 3] = whens[i];
   }
   const lineString = new LineString(null);
@@ -1081,8 +1079,8 @@ function readMultiGeometry(node, objectStack) {
   let multiGeometry;
   let homogeneous = true;
   const type = geometries[0].getType();
-  let geometry, i, ii;
-  for (i = 1, ii = geometries.length; i < ii; ++i) {
+  let geometry;
+  for (let i = 1, ii = geometries.length; i < ii; ++i) {
     geometry = geometries[i];
     if (geometry.getType() != type) {
       homogeneous = false;
@@ -1096,7 +1094,7 @@ function readMultiGeometry(node, objectStack) {
       const point = geometries[0];
       layout = point.getLayout();
       flatCoordinates = point.getFlatCoordinates();
-      for (i = 1, ii = geometries.length; i < ii; ++i) {
+      for (let i = 1, ii = geometries.length; i < ii; ++i) {
         geometry = geometries[i];
         extend(flatCoordinates, geometry.getFlatCoordinates());
       }
@@ -1171,13 +1169,11 @@ function readPolygon(node, objectStack) {
     const polygon = new Polygon(null);
     const flatCoordinates = flatLinearRings[0];
     const ends = [flatCoordinates.length];
-    let i, ii;
-    for (i = 1, ii = flatLinearRings.length; i < ii; ++i) {
+    for (let i = 1, ii = flatLinearRings.length; i < ii; ++i) {
       extend(flatCoordinates, flatLinearRings[i]);
       ends.push(flatCoordinates.length);
     }
-    polygon.setFlatCoordinates(
-      GeometryLayout.XYZ, flatCoordinates, ends);
+    polygon.setFlatCoordinates(GeometryLayout.XYZ, flatCoordinates, ends);
     polygon.setProperties(properties);
     return polygon;
   } else {
@@ -1251,16 +1247,15 @@ function readStyle(node, objectStack) {
  *     multiGeometry A multi-geometry.
  * @param {Array.<ol.geom.Geometry>} geometries List of geometries.
  */
-function setCommonGeometryProperties(multiGeometry,
-  geometries) {
+function setCommonGeometryProperties(multiGeometry, geometries) {
   const ii = geometries.length;
   const extrudes = new Array(geometries.length);
   const tessellates = new Array(geometries.length);
   const altitudeModes = new Array(geometries.length);
-  let geometry, i, hasExtrude, hasTessellate, hasAltitudeMode;
+  let hasExtrude, hasTessellate, hasAltitudeMode;
   hasExtrude = hasTessellate = hasAltitudeMode = false;
-  for (i = 0; i < ii; ++i) {
-    geometry = geometries[i];
+  for (let i = 0; i < ii; ++i) {
+    const geometry = geometries[i];
     extrudes[i] = geometry.get('extrude');
     tessellates[i] = geometry.get('tessellate');
     altitudeModes[i] = geometry.get('altitudeMode');
@@ -1846,8 +1841,7 @@ KML.prototype.readFeaturesFromNode = function(node, opt_options) {
     }
   } else if (localName == 'kml') {
     features = [];
-    let n;
-    for (n = node.firstElementChild; n; n = n.nextElementSibling) {
+    for (let n = node.firstElementChild; n; n = n.nextElementSibling) {
       const fs = this.readFeaturesFromNode(n, opt_options);
       if (fs) {
         extend(features, fs);
@@ -1886,8 +1880,7 @@ KML.prototype.readName = function(source) {
  * @return {string|undefined} Name.
  */
 KML.prototype.readNameFromDocument = function(doc) {
-  let n;
-  for (n = doc.firstChild; n; n = n.nextSibling) {
+  for (let n = doc.firstChild; n; n = n.nextSibling) {
     if (n.nodeType == Node.ELEMENT_NODE) {
       const name = this.readNameFromNode(n);
       if (name) {
@@ -1904,14 +1897,13 @@ KML.prototype.readNameFromDocument = function(doc) {
  * @return {string|undefined} Name.
  */
 KML.prototype.readNameFromNode = function(node) {
-  let n;
-  for (n = node.firstElementChild; n; n = n.nextElementSibling) {
+  for (let n = node.firstElementChild; n; n = n.nextElementSibling) {
     if (includes(NAMESPACE_URIS, n.namespaceURI) &&
         n.localName == 'name') {
       return readString(n);
     }
   }
-  for (n = node.firstElementChild; n; n = n.nextElementSibling) {
+  for (let n = node.firstElementChild; n; n = n.nextElementSibling) {
     const localName = n.localName;
     if (includes(NAMESPACE_URIS, n.namespaceURI) &&
         (localName == 'Document' ||
@@ -2078,8 +2070,7 @@ function writeColorTextNode(node, color) {
   const rgba = asArray(color);
   const opacity = (rgba.length == 4) ? rgba[3] : 1;
   const abgr = [opacity * 255, rgba[2], rgba[1], rgba[0]];
-  let i;
-  for (i = 0; i < 4; ++i) {
+  for (let i = 0; i < 4; ++i) {
     const hex = parseInt(abgr[i], 10).toString(16);
     abgr[i] = (hex.length == 1) ? '0' + hex : hex;
   }
@@ -2109,17 +2100,16 @@ function writeCoordinatesTextNode(node, coordinates, objectStack) {
     assert(false, 34); // Invalid geometry layout
   }
 
-  let d, i;
   const ii = coordinates.length;
   let text = '';
   if (ii > 0) {
     text += coordinates[0];
-    for (d = 1; d < dimension; ++d) {
+    for (let d = 1; d < dimension; ++d) {
       text += ',' + coordinates[d];
     }
-    for (i = stride; i < ii; i += stride) {
+    for (let i = stride; i < ii; i += stride) {
       text += ' ' + coordinates[i];
-      for (d = 1; d < dimension; ++d) {
+      for (let d = 1; d < dimension; ++d) {
         text += ',' + coordinates[i + d];
       }
     }
@@ -2501,8 +2491,7 @@ const GEOMETRY_TYPE_TO_NODENAME = {
  * @param {string=} opt_nodeName Node name.
  * @return {Node|undefined} Node.
  */
-const GEOMETRY_NODE_FACTORY = function(value, objectStack,
-  opt_nodeName) {
+const GEOMETRY_NODE_FACTORY = function(value, objectStack, opt_nodeName) {
   if (value) {
     const parentNode = objectStack[objectStack.length - 1].node;
     return createElementNS(parentNode.namespaceURI,
diff --git a/src/ol/format/MVT.js b/src/ol/format/MVT.js
index fa54a2dcff..9c9c82f9ae 100644
--- a/src/ol/format/MVT.js
+++ b/src/ol/format/MVT.js
@@ -372,12 +372,11 @@ MVT.prototype.readFeatures = function(source, opt_options) {
   const pbfLayers = pbf.readFields(layersPBFReader, {});
   /** @type {Array.<ol.Feature|ol.render.Feature>} */
   const features = [];
-  let pbfLayer;
   for (const name in pbfLayers) {
     if (layers && layers.indexOf(name) == -1) {
       continue;
     }
-    pbfLayer = pbfLayers[name];
+    const pbfLayer = pbfLayers[name];
 
     for (let i = 0, ii = pbfLayer.length; i < ii; ++i) {
       const rawFeature = readRawFeature(pbf, pbfLayer, i);
diff --git a/src/ol/format/Polyline.js b/src/ol/format/Polyline.js
index 43d07a73fc..70f59650f0 100644
--- a/src/ol/format/Polyline.js
+++ b/src/ol/format/Polyline.js
@@ -74,8 +74,7 @@ export function encodeDeltas(numbers, stride, opt_factor) {
     lastNumbers[d] = 0;
   }
 
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii;) {
+  for (let i = 0, ii = numbers.length; i < ii;) {
     for (d = 0; d < stride; ++d, ++i) {
       const num = numbers[i];
       const delta = num - lastNumbers[d];
@@ -112,8 +111,7 @@ export function decodeDeltas(encoded, stride, opt_factor) {
 
   const numbers = decodeFloats(encoded, factor);
 
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii;) {
+  for (let i = 0, ii = numbers.length; i < ii;) {
     for (d = 0; d < stride; ++d, ++i) {
       lastNumbers[d] += numbers[i];
 
@@ -139,8 +137,7 @@ export function decodeDeltas(encoded, stride, opt_factor) {
  */
 export function encodeFloats(numbers, opt_factor) {
   const factor = opt_factor ? opt_factor : 1e5;
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii; ++i) {
+  for (let i = 0, ii = numbers.length; i < ii; ++i) {
     numbers[i] = Math.round(numbers[i] * factor);
   }
 
@@ -160,8 +157,7 @@ export function encodeFloats(numbers, opt_factor) {
 export function decodeFloats(encoded, opt_factor) {
   const factor = opt_factor ? opt_factor : 1e5;
   const numbers = decodeSignedIntegers(encoded);
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii; ++i) {
+  for (let i = 0, ii = numbers.length; i < ii; ++i) {
     numbers[i] /= factor;
   }
   return numbers;
@@ -177,8 +173,7 @@ export function decodeFloats(encoded, opt_factor) {
  * @return {string} The encoded string.
  */
 export function encodeSignedIntegers(numbers) {
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii; ++i) {
+  for (let i = 0, ii = numbers.length; i < ii; ++i) {
     const num = numbers[i];
     numbers[i] = (num < 0) ? ~(num << 1) : (num << 1);
   }
@@ -194,8 +189,7 @@ export function encodeSignedIntegers(numbers) {
  */
 export function decodeSignedIntegers(encoded) {
   const numbers = decodeUnsignedIntegers(encoded);
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii; ++i) {
+  for (let i = 0, ii = numbers.length; i < ii; ++i) {
     const num = numbers[i];
     numbers[i] = (num & 1) ? ~(num >> 1) : (num >> 1);
   }
@@ -211,8 +205,7 @@ export function decodeSignedIntegers(encoded) {
  */
 export function encodeUnsignedIntegers(numbers) {
   let encoded = '';
-  let i, ii;
-  for (i = 0, ii = numbers.length; i < ii; ++i) {
+  for (let i = 0, ii = numbers.length; i < ii; ++i) {
     encoded += encodeUnsignedInteger(numbers[i]);
   }
   return encoded;
@@ -229,8 +222,7 @@ export function decodeUnsignedIntegers(encoded) {
   const numbers = [];
   let current = 0;
   let shift = 0;
-  let i, ii;
-  for (i = 0, ii = encoded.length; i < ii; ++i) {
+  for (let i = 0, ii = encoded.length; i < ii; ++i) {
     const b = encoded.charCodeAt(i) - 63;
     current |= (b & 0x1f) << shift;
     if (b < 0x20) {
diff --git a/src/ol/format/TopoJSON.js b/src/ol/format/TopoJSON.js
index 35a9cf83a7..53df71e8eb 100644
--- a/src/ol/format/TopoJSON.js
+++ b/src/ol/format/TopoJSON.js
@@ -78,9 +78,7 @@ function concatenateArcs(indices, arcs) {
   /** @type {Array.<ol.Coordinate>} */
   const coordinates = [];
   let index, arc;
-  let i, ii;
-  let j, jj;
-  for (i = 0, ii = indices.length; i < ii; ++i) {
+  for (let i = 0, ii = indices.length; i < ii; ++i) {
     index = indices[i];
     if (i > 0) {
       // splicing together arcs, discard last point
@@ -96,7 +94,7 @@ function concatenateArcs(indices, arcs) {
     coordinates.push.apply(coordinates, arc);
   }
   // provide fresh copies of coordinate arrays
-  for (j = 0, jj = coordinates.length; j < jj; ++j) {
+  for (let j = 0, jj = coordinates.length; j < jj; ++j) {
     coordinates[j] = coordinates[j].slice();
   }
   return coordinates;
@@ -130,9 +128,8 @@ function readPointGeometry(object, scale, translate) {
  */
 function readMultiPointGeometry(object, scale, translate) {
   const coordinates = object.coordinates;
-  let i, ii;
   if (scale && translate) {
-    for (i = 0, ii = coordinates.length; i < ii; ++i) {
+    for (let i = 0, ii = coordinates.length; i < ii; ++i) {
       transformVertex(coordinates[i], scale, translate);
     }
   }
@@ -162,8 +159,7 @@ function readLineStringGeometry(object, arcs) {
  */
 function readMultiLineStringGeometry(object, arcs) {
   const coordinates = [];
-  let i, ii;
-  for (i = 0, ii = object.arcs.length; i < ii; ++i) {
+  for (let i = 0, ii = object.arcs.length; i < ii; ++i) {
     coordinates[i] = concatenateArcs(object.arcs[i], arcs);
   }
   return new MultiLineString(coordinates);
@@ -179,8 +175,7 @@ function readMultiLineStringGeometry(object, arcs) {
  */
 function readPolygonGeometry(object, arcs) {
   const coordinates = [];
-  let i, ii;
-  for (i = 0, ii = object.arcs.length; i < ii; ++i) {
+  for (let i = 0, ii = object.arcs.length; i < ii; ++i) {
     coordinates[i] = concatenateArcs(object.arcs[i], arcs);
   }
   return new Polygon(coordinates);
@@ -196,13 +191,11 @@ function readPolygonGeometry(object, arcs) {
  */
 function readMultiPolygonGeometry(object, arcs) {
   const coordinates = [];
-  let polyArray, ringCoords, j, jj;
-  let i, ii;
-  for (i = 0, ii = object.arcs.length; i < ii; ++i) {
+  for (let i = 0, ii = object.arcs.length; i < ii; ++i) {
     // for each polygon
-    polyArray = object.arcs[i];
-    ringCoords = [];
-    for (j = 0, jj = polyArray.length; j < jj; ++j) {
+    const polyArray = object.arcs[i];
+    const ringCoords = [];
+    for (let j = 0, jj = polyArray.length; j < jj; ++j) {
       // for each ring
       ringCoords[j] = concatenateArcs(polyArray[j], arcs);
     }
@@ -229,8 +222,7 @@ function readMultiPolygonGeometry(object, arcs) {
 function readFeaturesFromGeometryCollection(collection, arcs, scale, translate, property, name, opt_options) {
   const geometries = collection.geometries;
   const features = [];
-  let i, ii;
-  for (i = 0, ii = geometries.length; i < ii; ++i) {
+  for (let i = 0, ii = geometries.length; i < ii; ++i) {
     features[i] = readFeatureFromGeometry(
       geometries[i], arcs, scale, translate, property, name, opt_options);
   }
@@ -294,8 +286,7 @@ TopoJSON.prototype.readFeatures;
 /**
  * @inheritDoc
  */
-TopoJSON.prototype.readFeaturesFromObject = function(
-  object, opt_options) {
+TopoJSON.prototype.readFeaturesFromObject = function(object, opt_options) {
   if (object.type == 'Topology') {
     const topoJSONTopology = /** @type {TopoJSONTopology} */ (object);
     let transform, scale = null, translate = null;
diff --git a/src/ol/format/WKT.js b/src/ol/format/WKT.js
index 5da81da3e8..aff1f9948a 100644
--- a/src/ol/format/WKT.js
+++ b/src/ol/format/WKT.js
@@ -611,8 +611,7 @@ function encodeMultiLineStringGeometry(geom) {
   const array = [];
   const components = geom.getLineStrings();
   for (let i = 0, ii = components.length; i < ii; ++i) {
-    array.push('(' + encodeLineStringGeometry(
-      components[i]) + ')');
+    array.push('(' + encodeLineStringGeometry(components[i]) + ')');
   }
   return array.join(',');
 }
@@ -626,8 +625,7 @@ function encodePolygonGeometry(geom) {
   const array = [];
   const rings = geom.getLinearRings();
   for (let i = 0, ii = rings.length; i < ii; ++i) {
-    array.push('(' + encodeLineStringGeometry(
-      rings[i]) + ')');
+    array.push('(' + encodeLineStringGeometry(rings[i]) + ')');
   }
   return array.join(',');
 }
@@ -641,8 +639,7 @@ function encodeMultiPolygonGeometry(geom) {
   const array = [];
   const components = geom.getPolygons();
   for (let i = 0, ii = components.length; i < ii; ++i) {
-    array.push('(' + encodePolygonGeometry(
-      components[i]) + ')');
+    array.push('(' + encodePolygonGeometry(components[i]) + ')');
   }
   return array.join(',');
 }
@@ -768,9 +765,8 @@ WKT.prototype.readFeaturesFromText = function(text, opt_options) {
     geometries = [geometry];
   }
   const features = [];
-  let feature;
   for (let i = 0, ii = geometries.length; i < ii; ++i) {
-    feature = new Feature();
+    const feature = new Feature();
     feature.setGeometry(geometries[i]);
     features.push(feature);
   }
diff --git a/src/ol/format/XMLFeature.js b/src/ol/format/XMLFeature.js
index 72accb915b..a35afd7504 100644
--- a/src/ol/format/XMLFeature.js
+++ b/src/ol/format/XMLFeature.js
@@ -44,8 +44,7 @@ XMLFeature.prototype.getType = function() {
  */
 XMLFeature.prototype.readFeature = function(source, opt_options) {
   if (isDocument(source)) {
-    return this.readFeatureFromDocument(
-      /** @type {Document} */ (source), opt_options);
+    return this.readFeatureFromDocument(/** @type {Document} */ (source), opt_options);
   } else if (isNode(source)) {
     return this.readFeatureFromNode(/** @type {Node} */ (source), opt_options);
   } else if (typeof source === 'string') {
@@ -107,12 +106,10 @@ XMLFeature.prototype.readFeatures = function(source, opt_options) {
  * @protected
  * @return {Array.<ol.Feature>} Features.
  */
-XMLFeature.prototype.readFeaturesFromDocument = function(
-  doc, opt_options) {
+XMLFeature.prototype.readFeaturesFromDocument = function(doc, opt_options) {
   /** @type {Array.<ol.Feature>} */
   const features = [];
-  let n;
-  for (n = doc.firstChild; n; n = n.nextSibling) {
+  for (let n = doc.firstChild; n; n = n.nextSibling) {
     if (n.nodeType == Node.ELEMENT_NODE) {
       extend(features, this.readFeaturesFromNode(n, opt_options));
     }