diff --git a/src/TileSource.coffee b/src/TileSource.coffee
deleted file mode 100644
index dd0e100..0000000
--- a/src/TileSource.coffee
+++ /dev/null
@@ -1,133 +0,0 @@
-###
-  termap - Terminal Map Viewer
-  by Michael Strassburger <codepoet@cpan.org>
-
-  Source for VectorTiles - supports
-  * remote TileServer
-  * local MBTiles and VectorTiles
-###
-
-Promise = require 'bluebird'
-userhome = require 'userhome'
-fetch = require 'node-fetch'
-fs = require 'fs'
-
-Tile = require './Tile'
-config = require './config'
-
-# https://github.com/mapbox/node-mbtiles has native build dependencies (sqlite3)
-# To maximize mapscii's compatibility, MBTiles support must be manually added via
-# $> npm install -g mbtiles
-MBTiles = try
-  require 'mbtiles'
-catch
-  null
-
-module.exports = class TileSource
-  cache: {}
-  cacheSize: 16
-  cached: []
-
-  modes:
-    MBTiles: 1
-    VectorTile: 2
-    HTTP: 3
-
-  mode: null
-  mbtiles: null
-  styler: null
-
-  init: (@source) ->
-    if @source.startsWith "http"
-      @_initPersistence() if config.persistDownloadedTiles
-
-      @mode = @modes.HTTP
-
-    else if @source.endsWith ".mbtiles"
-      unless MBTiles
-        throw new Error "MBTiles support must be installed with following command: 'npm install -g mbtiles'"
-
-      @mode = @modes.MBTiles
-      @loadMBtils source
-
-    else
-      throw new Error "source type isn't supported yet"
-
-  loadMBtils: (source) ->
-    new Promise (resolve, reject) =>
-      new MBTiles source, (err, @mbtiles) =>
-        if err then reject err
-        else resolve()
-
-  useStyler: (@styler) ->
-
-  getTile: (z, x, y) ->
-    unless @mode
-      throw new Error "no TileSource defined"
-
-    z = Math.max 0, Math.floor z
-
-    if cached = @cache[[z,x,y].join("-")]
-      return Promise.resolve cached
-
-    if @cached.length > @cacheSize
-      for tile in @cached.splice 0, Math.abs(@cacheSize-@cached.length)
-        delete @cache[tile]
-
-    switch @mode
-      when @modes.MBTiles then @_getMBTile z, x, y
-      when @modes.HTTP then @_getHTTP z, x, y
-
-  _getHTTP: (z, x, y) ->
-    promise =
-      if config.persistDownloadedTiles and tile = @_getPersited z, x, y
-        Promise.resolve tile
-      else
-        fetch @source+[z,x,y].join("/")+".pbf"
-        .then (res) => res.buffer()
-        .then (buffer) =>
-          @_persistTile z, x, y, buffer if config.persistDownloadedTiles
-          buffer
-
-    promise
-    .then (buffer) =>
-      @_createTile z, x, y, buffer
-
-  _getMBTile: (z, x, y) ->
-    new Promise (resolve, reject) =>
-      @mbtiles.getTile z, x, y, (err, buffer) =>
-        return reject err if err
-        resolve @_createTile z, x, y, buffer
-
-  _createTile: (z, x, y, buffer) ->
-    name = [z,x,y].join("-")
-    @cached.push name
-
-    tile = @cache[name] = new Tile @styler
-    tile.load buffer
-
-  _initPersistence: ->
-    try
-      @_createFolder userhome ".mapscii"
-      @_createFolder userhome ".mapscii", "cache"
-    catch error
-      config.persistDownloadedTiles = false
-      return
-
-  _persistTile: (z, x, y, buffer) ->
-    zoom = z.toString()
-    @_createFolder userhome ".mapscii", "cache", zoom
-    fs.writeFile userhome(".mapscii", "cache", zoom, "#{x}-#{y}.pbf"), buffer, -> null
-
-  _getPersited: (z, x, y) ->
-    try
-      fs.readFileSync userhome ".mapscii", "cache", z.toString(), "#{x}-#{y}.pbf"
-    catch error
-      false
-
-  _createFolder: (path) ->
-    try
-      fs.mkdirSync path
-      true
-    catch e
-      e.code is "EEXIST"
diff --git a/src/TileSource.js b/src/TileSource.js
new file mode 100644
index 0000000..314ce49
--- /dev/null
+++ b/src/TileSource.js
@@ -0,0 +1,180 @@
+/*
+  termap - Terminal Map Viewer
+  by Michael Strassburger <codepoet@cpan.org>
+
+  Source for VectorTiles - supports
+  * remote TileServer
+  * local MBTiles and VectorTiles
+*/
+'use strict';
+const userhome = require('userhome');
+const fetch = require('node-fetch');
+const fs = require('fs');
+
+const Tile = require('./Tile');
+const config = require('./config');
+
+// https://github.com/mapbox/node-mbtiles has native build dependencies (sqlite3)
+// To maximize mapscii's compatibility, MBTiles support must be manually added via
+// $> npm install -g mbtiles
+let MBTiles = null;
+try {
+  MBTiles = require('mbtiles');
+} catch (err) {}
+
+const cache = {};
+const cacheSize = 16;
+const cached = [];
+
+const modes = {
+  MBTiles: 1,
+  VectorTile: 2,
+  HTTP: 3,
+};
+
+class TileSource {
+  init(source) {
+    this.source = source;
+    
+    this.cache = {};
+    this.cacheSize = 16;
+    this.cached = [];
+    
+    this.mode = null;
+    this.mbtiles = null;
+    this.styler = null;
+    
+    if (this.source.startsWith('http')) {
+      if (config.persistDownloadedTiles) {
+        this._initPersistence();
+      }
+
+      this.mode = modes.HTTP;
+
+    } else if (this.source.endsWith('.mbtiles')) {
+      if (!MBTiles) {
+        throw new Error("MBTiles support must be installed with following command: 'npm install -g mbtiles'");
+      }
+
+      this.mode = modes.MBTiles;
+      this.loadMBtils(source);
+    } else {
+      throw new Error("source type isn't supported yet");
+    }
+  }
+
+  loadMBtils(source) {
+    return new Promise((resolve, reject) => {
+      new MBTiles(source, (err, mbtiles) => {
+        if (err) {
+          reject(err);
+        }
+        this.mbtiles = mbtiles;
+        resolve();
+      });
+    });
+  }
+
+  useStyler(styler) {
+    this.styler = styler;
+  }
+
+  getTile(z, x, y) {
+    if (!this.mode) {
+      throw new Error("no TileSource defined");
+    }
+    
+    const cached = this.cache[[z, x, y].join("-")];
+    if (cached) {
+      return Promise.resolve(cached);
+    }
+    
+    if (this.cached.length > this.cacheSize) {
+      const overflow = Math.abs(this.cacheSize - this.cache.length);
+      for (const tile in this.cached.splice(0, overflow)) {
+        delete this.cache[tile];
+      }
+    }
+  
+    switch (this.mode) {
+      case modes.MBTiles:
+        return this._getMBTile(z, x, y);
+      case modes.HTTP:
+        return this._getHTTP(z, x, y);
+    }
+  }
+
+  _getHTTP(z, x, y) {
+    let promise;
+    const persistedTile = this._getPersited(z, x, y);
+    if (config.persistDownloadedTiles && persistedTile) {
+      promise = Promise.resolve(persistedTile);
+    } else {
+      promise = fetch(this.source + [z,x,y].join('/') + '.pbf')
+      .then((res) => res.buffer())
+      .then((buffer) => {
+        if (config.persistDownloadedTiles) {
+          this._persistTile(z, x, y, buffer);
+          return buffer;
+        }
+      });
+    }
+    return promise.then((buffer) => {
+      return this._createTile(z, x, y, buffer);
+    });
+  }
+
+  _getMBTile(z, x, y) {
+    return new Promise((resolve, reject) => {
+      this.mbtiles.getTile(z, x, y, (err, buffer) => {
+        if (err) {
+          reject(err);
+        }
+        resolve(this._createTile(z, x, y, buffer));
+      });
+    });
+  }
+
+  _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);
+  }
+
+  _initPersistence() {
+    try {
+      this._createFolder(userhome('.mapscii'));
+      this._createFolder(userhome('.mapscii', 'cache'));
+    } catch (error) {
+      config.persistDownloadedTiles = false;
+    }
+  }
+
+  _persistTile(z, x, y, buffer) {
+    const zoom = z.toString();
+    this._createFolder(userhome('.mapscii', 'cache', zoom));
+    const filePath = userhome('.mapscii', 'cache', zoom, `${x}-${y}.pbf`);
+    return fs.writeFile(filePath, buffer, () => null);
+  }
+
+  _getPersited(z, x, y) {
+    try {
+      return fs.readFileSync(userhome('.mapscii', 'cache', z.toString(), `${x}-${y}.pbf`));
+    } catch (error) {
+      return false;
+    }
+  }
+
+  _createFolder(path) {
+    try {
+      fs.mkdirSync(path);
+      return true;
+    } catch (error) {
+      return error.code === "EEXIST";
+    }
+  }
+}
+
+module.exports = TileSource;