Reduce code complexity

src/BrailleBuffer.js

@@ -113,9 +113,8 @@ export default class BrailleBuffer {
     }
 
     //TODO Optimize this part
-    var i, k;
     const results = [];
-    for (i = k = 1; k <= 255; i = ++k) {
+    for (let i = 1; i <= 255; i++) {
       const braille = (i & 7) + ((i & 56) << 1) + ((i & 64) >> 3) + (i & 128);
       results.push(this.asciiToBraille[i] = masks.reduce((function(best, mask) {
         const covered = utils.population(mask.mask & braille);

src/Canvas.js

@@ -163,9 +163,8 @@ export default class Canvas {
     const b = this._bresenham(pointA, pointC);
     const c = this._bresenham(pointA, pointB);
     
-    const points = a.concat(b).concat(c).filter((point) => {
-      var ref;
-      return (0 <= (ref = point.y) && ref < this.height);
+    const points = a.concat(b).concat(c).filter(({y}) => {
+      return 0 <= y && y < this.height;
     }).sort(function(a, b) {
       if (a.y === b.y) {
         return a.x - b.x;

src/Styler.js

@@ -13,7 +13,6 @@ export default class Styler {
   constructor(style) {
     this.styleById = {};
     this.styleByLayer = {};
-    var base, name;
     this.styleName = style.name;
     if (style.constants) {
       this._replaceConstants(style.constants, style.layers);
@@ -30,10 +29,7 @@ export default class Styler {
 
       layer.appliesTo = this._compileFilter(layer.filter);
 
-      //TODO Better translation of: @styleByLayer[style['source-layer']] ?= []
-      if ((base = this.styleByLayer)[name = layer['source-layer']] == null) {
-        base[name] = [];
-      }
+      this.styleByLayer[layer['source-layer']] ??= [];
       this.styleByLayer[layer['source-layer']].push(layer);
       this.styleById[layer.id] = layer;
     }

src/Tile.js

@@ -18,14 +18,10 @@ export default class Tile {
     this.styler = styler;
   }
 
-  load(buffer) {
-    return this._unzipIfNeeded(buffer).then((buffer) => {
-      return this._loadTile(buffer);
-    }).then(() => {
-      return this._loadLayers();
-    }).then(() => {
-      return this;
-    });
+  async load(buffer) {
+    const unzippedBuffer = await this._unzipIfNeeded(buffer);
+    await this._loadTile(unzippedBuffer);
+    await this._loadLayers();
   }
 
   _loadTile(buffer) {

src/TileSource.js

@@ -133,12 +133,13 @@ export default class TileSource {
     });
   }
 
-  _createTile(z, x, y, buffer) {
+  async _createTile(z, x, y, buffer) {
     const name = [z, x, y].join('-');
     this.cached.push(name);
     
     const tile = this.cache[name] = new Tile(this.styler);
-    return tile.load(buffer);
+    await tile.load(buffer);
+    return tile;
   }
 
   _initPersistence() {