Enable eslint prefer-const rule

Fixes were made manually.

.eslintrc

@@ -12,6 +12,7 @@
     "no-warning-comments": "error",
     "object-curly-spacing": "off",
     "prefer-arrow-callback": "error",
+    "prefer-const": "error",
     "prefer-template": "error",
     "quotes": "off",
     "space-before-function-paren": "off",

js/data/bucket/line_bucket.js

@@ -122,7 +122,7 @@ LineBucket.prototype.addLine = function(vertices, featureProperties, join, cap,
 
     const sharpCornerOffset = SHARP_CORNER_OFFSET * (EXTENT / (512 * this.overscaling));
 
-    let firstVertex = vertices[0],
+    const firstVertex = vertices[0],
         lastVertex = vertices[len - 1],
         closed = firstVertex.equals(lastVertex);
 
@@ -135,10 +135,10 @@ LineBucket.prototype.addLine = function(vertices, featureProperties, join, cap,
 
     this.distance = 0;
 
-    let beginCap = cap,
-        endCap = closed ? 'butt' : cap,
-        startOfLine = true,
-        currentVertex, prevVertex, nextVertex, prevNormal, nextNormal, offsetA, offsetB;
+    const beginCap = cap,
+        endCap = closed ? 'butt' : cap;
+    let startOfLine = true;
+    let currentVertex, prevVertex, nextVertex, prevNormal, nextNormal, offsetA, offsetB;
 
     // the last three vertices added
     this.e1 = this.e2 = this.e3 = -1;

js/data/bucket/symbol_bucket.js

@@ -266,7 +266,7 @@ SymbolBucket.prototype.addFeature = function(lines, shapedText, shapedIcon, feat
 
     const glyphSize = 24;
 
-    let fontScale = this.adjustedTextSize / glyphSize,
+    const fontScale = this.adjustedTextSize / glyphSize,
         textMaxSize = this.adjustedTextMaxSize !== undefined ? this.adjustedTextMaxSize : this.adjustedTextSize,
         textBoxScale = this.tilePixelRatio * fontScale,
         textMaxBoxScale = this.tilePixelRatio * textMaxSize / glyphSize,
@@ -416,7 +416,7 @@ SymbolBucket.prototype.placeFeatures = function(collisionTile, showCollisionBoxe
 
         const angle = collisionTile.angle;
 
-        let sin = Math.sin(angle),
+        const sin = Math.sin(angle),
             cos = Math.cos(angle);
 
         this.sortedSymbolInstances = symbolInstancesStructTypeArray.sort((a, b) => {
@@ -440,7 +440,7 @@ SymbolBucket.prototype.placeFeatures = function(collisionTile, showCollisionBoxe
         const hasText = !(symbolInstance.textBoxStartIndex === symbolInstance.textBoxEndIndex);
         const hasIcon = !(symbolInstance.iconBoxStartIndex === symbolInstance.iconBoxEndIndex);
 
-        let iconWithoutText = layout['text-optional'] || !hasText,
+        const iconWithoutText = layout['text-optional'] || !hasText,
             textWithoutIcon = layout['icon-optional'] || !hasIcon;
 
 
@@ -507,15 +507,15 @@ SymbolBucket.prototype.addSymbols = function(programName, quadsStart, quadsEnd,
         const a = (symbol.anchorAngle + placementAngle + Math.PI) % (Math.PI * 2);
         if (keepUpright && alongLine && (a <= Math.PI / 2 || a > Math.PI * 3 / 2)) continue;
 
-        let tl = symbol.tl,
+        const tl = symbol.tl,
             tr = symbol.tr,
             bl = symbol.bl,
             br = symbol.br,
             tex = symbol.tex,
-            anchorPoint = symbol.anchorPoint,
+            anchorPoint = symbol.anchorPoint;
 
-            minZoom = Math.max(zoom + Math.log(symbol.minScale) / Math.LN2, placementZoom),
-            maxZoom = Math.min(zoom + Math.log(symbol.maxScale) / Math.LN2, 25);
+        let minZoom = Math.max(zoom + Math.log(symbol.minScale) / Math.LN2, placementZoom);
+        const maxZoom = Math.min(zoom + Math.log(symbol.maxScale) / Math.LN2, 25);
 
         if (maxZoom <= minZoom) continue;
 
@@ -550,7 +550,7 @@ SymbolBucket.prototype.updateIcons = function(icons) {
 
 SymbolBucket.prototype.updateFont = function(stacks) {
     this.recalculateStyleLayers();
-    let fontName = this.layer.layout['text-font'],
+    const fontName = this.layer.layout['text-font'],
         stack = stacks[fontName] = stacks[fontName] || {};
 
     this.textFeatures = resolveText(this.features, this.layer.layout, stack);
@@ -600,19 +600,19 @@ SymbolBucket.prototype.addSymbolInstance = function(anchor, line, shapedText, sh
     textBoxScale, textPadding, textAlongLine,
     iconBoxScale, iconPadding, iconAlongLine, globalProperties, featureProperties) {
 
-    let glyphQuadStartIndex, glyphQuadEndIndex, iconQuadStartIndex, iconQuadEndIndex, textCollisionFeature, iconCollisionFeature, glyphQuads, iconQuads;
+    let textCollisionFeature, iconCollisionFeature, glyphQuads, iconQuads;
     if (shapedText) {
         glyphQuads = addToBuffers ? getGlyphQuads(anchor, shapedText, textBoxScale, line, layer, textAlongLine) : [];
         textCollisionFeature = new CollisionFeature(collisionBoxArray, line, anchor, featureIndex, sourceLayerIndex, bucketIndex, shapedText, textBoxScale, textPadding, textAlongLine, false);
     }
 
-    glyphQuadStartIndex = this.symbolQuadsArray.length;
+    const glyphQuadStartIndex = this.symbolQuadsArray.length;
     if (glyphQuads && glyphQuads.length) {
         for (let i = 0; i < glyphQuads.length; i++) {
             this.addSymbolQuad(glyphQuads[i]);
         }
     }
-    glyphQuadEndIndex = this.symbolQuadsArray.length;
+    const glyphQuadEndIndex = this.symbolQuadsArray.length;
 
     const textBoxStartIndex = textCollisionFeature ? textCollisionFeature.boxStartIndex : this.collisionBoxArray.length;
     const textBoxEndIndex = textCollisionFeature ? textCollisionFeature.boxEndIndex : this.collisionBoxArray.length;
@@ -622,11 +622,11 @@ SymbolBucket.prototype.addSymbolInstance = function(anchor, line, shapedText, sh
         iconCollisionFeature = new CollisionFeature(collisionBoxArray, line, anchor, featureIndex, sourceLayerIndex, bucketIndex, shapedIcon, iconBoxScale, iconPadding, iconAlongLine, true);
     }
 
-    iconQuadStartIndex = this.symbolQuadsArray.length;
+    const iconQuadStartIndex = this.symbolQuadsArray.length;
     if (iconQuads && iconQuads.length === 1) {
         this.addSymbolQuad(iconQuads[0]);
     }
-    iconQuadEndIndex = this.symbolQuadsArray.length;
+    const iconQuadEndIndex = this.symbolQuadsArray.length;
 
     const iconBoxStartIndex = iconCollisionFeature ? iconCollisionFeature.boxStartIndex : this.collisionBoxArray.length;
     const iconBoxEndIndex = iconCollisionFeature ? iconCollisionFeature.boxEndIndex : this.collisionBoxArray.length;

js/data/feature_index.js

@@ -104,7 +104,7 @@ FeatureIndex.prototype.query = function(args, styleLayers) {
 
     const result = {};
 
-    let params = args.params || {},
+    const params = args.params || {},
         pixelsToTileUnits = EXTENT / args.tileSize / args.scale,
         filter = featureFilter(params.filter);
 

js/geo/lng_lat_bounds.js

@@ -65,9 +65,9 @@ LngLatBounds.prototype = {
      * @returns {LngLatBounds} `this`
      */
     extend: function(obj) {
-        let sw = this._sw,
-            ne = this._ne,
-            sw2, ne2;
+        const sw = this._sw,
+            ne = this._ne;
+        let sw2, ne2;
 
         if (obj instanceof LngLat) {
             sw2 = obj;

js/geo/transform.js

@@ -1,6 +1,6 @@
 'use strict';
 
-let LngLat = require('./lng_lat'),
+const LngLat = require('./lng_lat'),
     Point = require('point-geometry'),
     Coordinate = require('./coordinate'),
     util = require('../util/util'),
@@ -9,7 +9,7 @@ let LngLat = require('./lng_lat'),
     EXTENT = require('../data/bucket').EXTENT,
     glmatrix = require('gl-matrix');
 
-let vec4 = glmatrix.vec4,
+const vec4 = glmatrix.vec4,
     mat4 = glmatrix.mat4,
     mat2 = glmatrix.mat2;
 
@@ -160,7 +160,7 @@ Transform.prototype = {
         if (z < options.minzoom) return [];
         if (z > options.maxzoom) z = options.maxzoom;
 
-        let tr = this,
+        const tr = this,
             tileCenter = tr.locationCoordinate(tr.center)._zoomTo(z),
             centerPoint = new Point(tileCenter.column - 0.5, tileCenter.row - 0.5);
 
@@ -278,7 +278,7 @@ Transform.prototype = {
      * @private
      */
     locationCoordinate: function(lnglat) {
-        let k = this.zoomScale(this.tileZoom) / this.worldSize,
+        const k = this.zoomScale(this.tileZoom) / this.worldSize,
             ll = LngLat.convert(lnglat);
 
         return new Coordinate(
@@ -377,8 +377,8 @@ Transform.prototype = {
 
         this._constraining = true;
 
-        let minY, maxY, minX, maxX, sy, sx, x2, y2,
-            size = this.size,
+        let minY, maxY, minX, maxX, sy, sx, x2, y2;
+        const size = this.size,
             unmodified = this._unmodified;
 
         if (this.latRange) {
@@ -407,15 +407,15 @@ Transform.prototype = {
         }
 
         if (this.latRange) {
-            let y = this.y,
+            const y = this.y,
                 h2 = size.y / 2;
 
             if (y - h2 < minY) y2 = minY + h2;
             if (y + h2 > maxY) y2 = maxY - h2;
         }
 
         if (this.lngRange) {
-            let x = this.x,
+            const x = this.x,
                 w2 = size.x / 2;
 
             if (x - w2 < minX) x2 = minX + w2;

js/lib/debugtext.js

@@ -103,8 +103,8 @@ const simplexFont = {
 module.exports = function textVertices(text, left, baseline, scale) {
     scale = scale || 1;
 
-    let strokes = [],
-        i, len, j, len2, glyph, x, y, prev;
+    const strokes = [];
+    let i, len, j, len2, glyph, x, y, prev;
 
     for (i = 0, len = text.length; i < len; i++) {
         glyph = simplexFont[text[i]];

js/render/draw_extrusion.js

@@ -197,7 +197,7 @@ function setLight(program, painter) {
     const gl = painter.gl;
     const light = painter.style.light;
 
-    let _lp = light.calculated.position,
+    const _lp = light.calculated.position,
         lightPos = [_lp.x, _lp.y, _lp.z];
     const lightMat = mat3.create();
     if (light.calculated.anchor === 'viewport') mat3.fromRotation(lightMat, -painter.transform.angle);

js/render/draw_raster.js

@@ -54,7 +54,7 @@ function drawRasterTile(painter, sourceCache, layer, coord) {
     gl.uniform1f(program.u_contrast_factor, contrastFactor(layer.paint['raster-contrast']));
     gl.uniform3fv(program.u_spin_weights, spinWeights(layer.paint['raster-hue-rotate']));
 
-    let parentTile = tile.sourceCache && tile.sourceCache.findLoadedParent(coord, 0, {}),
+    const parentTile = tile.sourceCache && tile.sourceCache.findLoadedParent(coord, 0, {}),
         opacities = getOpacities(tile, parentTile, layer, painter.transform);
 
     let parentScaleBy, parentTL;

js/source/geojson_worker_source.js

@@ -36,7 +36,7 @@ GeoJSONWorkerSource.prototype = util.inherit(VectorTileWorkerSource, /** @lends
      * See {@link VectorTileWorkerSource#loadTile}.
      */
     loadVectorData: function (params, callback) {
-        let source = params.source,
+        const source = params.source,
             coord = params.coord;
 
         if (!this._geoJSONIndexes[source]) {

js/source/geojson_wrapper.js

@@ -36,7 +36,7 @@ FeatureWrapper.prototype.loadGeometry = function() {
     this.geometry = [];
 
     for (let i = 0; i < rings.length; i++) {
-        let ring = rings[i],
+        const ring = rings[i],
             newRing = [];
         for (let j = 0; j < ring.length; j++) {
             newRing.push(new Point(ring[j][0], ring[j][1]));
@@ -49,8 +49,8 @@ FeatureWrapper.prototype.loadGeometry = function() {
 FeatureWrapper.prototype.bbox = function() {
     if (!this.geometry) this.loadGeometry();
 
-    let rings = this.geometry,
-        x1 = Infinity,
+    const rings = this.geometry;
+    let x1 = Infinity,
         x2 = -Infinity,
         y1 = Infinity,
         y2 = -Infinity;

js/source/tile_coord.js

@@ -42,9 +42,9 @@ TileCoord.prototype.toCoordinate = function(sourceMaxZoom) {
 
 // Parse a packed integer id into a TileCoord object
 TileCoord.fromID = function(id) {
-    let z = id % 32, dim = 1 << z;
+    const z = id % 32, dim = 1 << z;
     const xy = ((id - z) / 32);
-    let x = xy % dim, y = ((xy - x) / dim) % dim;
+    const x = xy % dim, y = ((xy - x) / dim) % dim;
     let w = Math.floor(xy / (dim * dim));
     if (w % 2 !== 0) w = w * -1 - 1;
     w /= 2;

js/source/vector_tile_worker_source.js

@@ -43,7 +43,7 @@ VectorTileWorkerSource.prototype = {
      * @param {boolean} params.showCollisionBoxes
      */
     loadTile: function(params, callback) {
-        let source = params.source,
+        const source = params.source,
             uid = params.uid;
 
         if (!this.loading[source])
@@ -81,7 +81,7 @@ VectorTileWorkerSource.prototype = {
      * @param {string} params.uid The UID for this tile.
      */
     reloadTile: function(params, callback) {
-        let loaded = this.loaded[params.source],
+        const loaded = this.loaded[params.source],
             uid = params.uid;
         if (loaded && loaded[uid]) {
             const workerTile = loaded[uid];
@@ -97,7 +97,7 @@ VectorTileWorkerSource.prototype = {
      * @param {string} params.uid The UID for this tile.
      */
     abortTile: function(params) {
-        let loading = this.loading[params.source],
+        const loading = this.loading[params.source],
             uid = params.uid;
         if (loading && loading[uid] && loading[uid].abort) {
             loading[uid].abort();
@@ -113,7 +113,7 @@ VectorTileWorkerSource.prototype = {
      * @param {string} params.uid The UID for this tile.
      */
     removeTile: function(params) {
-        let loaded = this.loaded[params.source],
+        const loaded = this.loaded[params.source],
             uid = params.uid;
         if (loaded && loaded[uid]) {
             delete loaded[uid];
@@ -157,7 +157,7 @@ VectorTileWorkerSource.prototype = {
     },
 
     redoPlacement: function(params, callback) {
-        let loaded = this.loaded[params.source],
+        const loaded = this.loaded[params.source],
             loading = this.loading[params.source],
             uid = params.uid;
 

js/source/worker_tile.js

@@ -106,7 +106,7 @@ WorkerTile.prototype.parse = function(data, layerFamilies, actor, callback) {
         }
     }
 
-    let buckets = [],
+    const buckets = [],
         symbolBuckets = this.symbolBuckets = [],
         otherBuckets = [];
 

js/style/light.js

@@ -70,7 +70,7 @@ Light.prototype = util.inherit(Evented, {
 
     getLightValue: function(property, globalProperties) {
         if (property === 'position') {
-            let calculated = this._transitions[property].calculate(globalProperties),
+            const calculated = this._transitions[property].calculate(globalProperties),
                 cartesian = util.sphericalToCartesian(calculated);
             return {
                 x: cartesian[0],

js/style/style.js

@@ -765,9 +765,9 @@ Style.prototype = util.inherit(Evented, {
     },
 
     'get glyphs': function(mapId, params, callback) {
-        let stacks = params.stacks,
-            remaining = Object.keys(stacks).length,
-            allGlyphs = {};
+        const stacks = params.stacks;
+        let remaining = Object.keys(stacks).length;
+        const allGlyphs = {};
 
         for (const fontName in stacks) {
             this.glyphSource.getSimpleGlyphs(fontName, stacks[fontName], params.uid, done);

js/symbol/collision_tile.js

@@ -32,7 +32,7 @@ function CollisionTile(angle, pitch, collisionBoxArray) {
     this.angle = angle;
     this.pitch = pitch;
 
-    let sin = Math.sin(angle),
+    const sin = Math.sin(angle),
         cos = Math.cos(angle);
     this.rotationMatrix = [cos, -sin, sin, cos];
     this.reverseRotationMatrix = [cos, sin, -sin, cos];

js/symbol/get_anchors.js

@@ -59,16 +59,16 @@ function resample(line, offset, spacing, angleWindowSize, maxAngle, labelLength,
 
     for (let i = 0; i < line.length - 1; i++) {
 
-        let a = line[i],
+        const a = line[i],
             b = line[i + 1];
 
-        let segmentDist = a.dist(b),
+        const segmentDist = a.dist(b),
             angle = b.angleTo(a);
 
         while (markedDistance + spacing < distance + segmentDist) {
             markedDistance += spacing;
 
-            let t = (markedDistance - distance) / segmentDist,
+            const t = (markedDistance - distance) / segmentDist,
                 x = interpolate(a.x, b.x, t),
                 y = interpolate(a.y, b.y, t);