diff --git a/src/OpenStreetBrowserLoader.js b/src/OpenStreetBrowserLoader.js
index e8659ed9..4b163a1b 100644
--- a/src/OpenStreetBrowserLoader.js
+++ b/src/OpenStreetBrowserLoader.js
@@ -2,268 +2,270 @@ var OverpassLayer = require('overpass-layer')
 
 const Repository = require('./Repository')
 
-function OpenStreetBrowserLoader () {
-  this.types = {}
-  this.categories = {}
-  this.repoCache = {}
-  this.repositories = {}
-  this.templates = {}
-  this._loadClash = {} // if a category is being loaded multiple times, collect callbacks
-}
-
-OpenStreetBrowserLoader.prototype.setMap = function (map) {
-  this.map = map
-}
-
-/**
- * @param string id ID of the category
- * @param [object] options Options.
- * @waram {boolean} [options.force=false] Whether repository should be reload or not.
- * @param function callback Callback which will be called with (err, category)
- */
-OpenStreetBrowserLoader.prototype.getCategory = function (id, options, callback) {
-  if (typeof options === 'function') {
-    callback = options
-    options = {}
+class OpenStreetBrowserLoader {
+  constructor () {
+    this.types = {}
+    this.categories = {}
+    this.repoCache = {}
+    this.repositories = {}
+    this.templates = {}
+    this._loadClash = {} // if a category is being loaded multiple times, collect callbacks
   }
 
-  var ids = this.getFullId(id, options)
-  if (ids === null) {
-    return callback(new Error('invalid id'), null)
+  setMap (map) {
+    this.map = map
   }
 
-  if (options.force) {
-    delete this.categories[ids.fullId]
-  }
+  /**
+   * @param string id ID of the category
+   * @param [object] options Options.
+   * @waram {boolean} [options.force=false] Whether repository should be reload or not.
+   * @param function callback Callback which will be called with (err, category)
+   */
+  getCategory (id, options, callback) {
+    if (typeof options === 'function') {
+      callback = options
+      options = {}
+    }
 
-  if (ids.fullId in this.categories) {
-    return callback(null, this.categories[ids.fullId])
-  }
+    var ids = this.getFullId(id, options)
+    if (ids === null) {
+      return callback(new Error('invalid id'), null)
+    }
 
-  var opt = JSON.parse(JSON.stringify(options))
-  opt.categoryId = ids.entityId
-  opt.repositoryId = ids.repositoryId
+    if (options.force) {
+      delete this.categories[ids.fullId]
+    }
 
-  this.getRepo(ids.repositoryId, opt, function (err, repoData) {
-    // maybe loaded in the meantime?
     if (ids.fullId in this.categories) {
       return callback(null, this.categories[ids.fullId])
     }
 
-    if (err) {
-      return callback(err, null)
-    }
+    var opt = JSON.parse(JSON.stringify(options))
+    opt.categoryId = ids.entityId
+    opt.repositoryId = ids.repositoryId
 
-    if (!(ids.entityId in repoData.categories)) {
-      return callback(new Error('category "' + ids.entityId + '" not defined'), null)
-    }
+    this.getRepo(ids.repositoryId, opt, function (err, repoData) {
+      // maybe loaded in the meantime?
+      if (ids.fullId in this.categories) {
+        return callback(null, this.categories[ids.fullId])
+      }
 
-    this.getCategoryFromData(ids.id, opt, repoData.categories[ids.entityId], function (err, category) {
-      if (category) {
-        category.setMap(this.map)
+      if (err) {
+        return callback(err, null)
       }
 
-      callback(err, category)
-    }.bind(this))
-  }.bind(this))
-}
+      if (!(ids.entityId in repoData.categories)) {
+        return callback(new Error('category "' + ids.entityId + '" not defined'), null)
+      }
 
-/**
- * @param string repo ID of the repository
- * @parapm [object] options Options.
- * @waram {boolean} [options.force=false] Whether repository should be reload or not.
- * @param function callback Callback which will be called with (err, repoData)
- */
-OpenStreetBrowserLoader.prototype.getRepo = function (repo, options, callback) {
-  if (options.force) {
-    delete this.repoCache[repo]
-  }
+      this.getCategoryFromData(ids.id, opt, repoData.categories[ids.entityId], function (err, category) {
+        if (category) {
+          category.setMap(this.map)
+        }
 
-  if (repo in this.repoCache) {
-    return callback.apply(this, this.repoCache[repo])
+        callback(err, category)
+      }.bind(this))
+    }.bind(this))
   }
 
-  if (repo in this._loadClash) {
-    this._loadClash[repo].push(callback)
-    return
-  }
+  /**
+   * @param string repo ID of the repository
+   * @parapm [object] options Options.
+   * @waram {boolean} [options.force=false] Whether repository should be reload or not.
+   * @param function callback Callback which will be called with (err, repoData)
+   */
+  getRepo (repo, options, callback) {
+    if (options.force) {
+      delete this.repoCache[repo]
+    }
 
-  this._loadClash[repo] = [ callback ]
+    if (repo in this.repoCache) {
+      return callback.apply(this, this.repoCache[repo])
+    }
 
-  function reqListener (req) {
-    if (req.status !== 200) {
-      console.log('http error when loading repository', req)
-      this.repoCache[repo] = [ req.statusText, null ]
-    } else {
-      try {
-        let repoData = JSON.parse(req.responseText)
-        this.repositories[repo] = new Repository(repo, repoData)
-        this.repoCache[repo] = [ null,  repoData ]
-      } catch (err) {
-        console.log('couldn\'t parse repository', req.responseText)
-        this.repoCache[repo] = [ 'couldn\t parse repository', null ]
-      }
+    if (repo in this._loadClash) {
+      this._loadClash[repo].push(callback)
+      return
     }
 
-    var todo = this._loadClash[repo]
-    delete this._loadClash[repo]
+    this._loadClash[repo] = [ callback ]
+
+    function reqListener (req) {
+      if (req.status !== 200) {
+        console.log('http error when loading repository', req)
+        this.repoCache[repo] = [ req.statusText, null ]
+      } else {
+        try {
+          let repoData = JSON.parse(req.responseText)
+          this.repositories[repo] = new Repository(repo, repoData)
+          this.repoCache[repo] = [ null,  repoData ]
+        } catch (err) {
+          console.log('couldn\'t parse repository', req.responseText)
+          this.repoCache[repo] = [ 'couldn\t parse repository', null ]
+        }
+      }
 
-    todo.forEach(function (callback) {
-      callback.apply(this, this.repoCache[repo])
-    }.bind(this))
-  }
+      var todo = this._loadClash[repo]
+      delete this._loadClash[repo]
 
-  var param = []
-  if (repo) {
-    param.push('repo=' + encodeURIComponent(repo))
-  }
-  param.push('lang=' + encodeURIComponent(ui_lang))
-  param.push(config.categoriesRev)
-  param = param.length ? '?' + param.join('&') : ''
-
-  var req = new XMLHttpRequest()
-  req.addEventListener('load', reqListener.bind(this, req))
-  req.open('GET', 'repo.php' + param)
-  req.send()
-}
+      todo.forEach(function (callback) {
+        callback.apply(this, this.repoCache[repo])
+      }.bind(this))
+    }
 
-OpenStreetBrowserLoader.prototype.getRepository = function (id, options, callback) {
-  if (id in this.repositories) {
-    return callback(null, this.repositories[id])
+    var param = []
+    if (repo) {
+      param.push('repo=' + encodeURIComponent(repo))
+    }
+    param.push('lang=' + encodeURIComponent(ui_lang))
+    param.push(config.categoriesRev)
+    param = param.length ? '?' + param.join('&') : ''
+
+    var req = new XMLHttpRequest()
+    req.addEventListener('load', reqListener.bind(this, req))
+    req.open('GET', 'repo.php' + param)
+    req.send()
   }
 
-  this.getRepo(id, options, (err, repoData) => {
-    if (err) {
-      return callback(err)
+  getRepository (id, options, callback) {
+    if (id in this.repositories) {
+      return callback(null, this.repositories[id])
     }
 
-    callback(null, this.repositories[id])
-  })
-}
+    this.getRepo(id, options, (err, repoData) => {
+      if (err) {
+        return callback(err)
+      }
 
-/**
- * @param string id ID of the template
- * @parapm [object] options Options.
- * @waram {boolean} [options.force=false] Whether repository should be reload or not.
- * @param function callback Callback which will be called with (err, template)
- */
-OpenStreetBrowserLoader.prototype.getTemplate = function (id, options, callback) {
-  if (typeof options === 'function') {
-    callback = options
-    options = {}
+      callback(null, this.repositories[id])
+    })
   }
 
-  var ids = this.getFullId(id, options)
+  /**
+   * @param string id ID of the template
+   * @parapm [object] options Options.
+   * @waram {boolean} [options.force=false] Whether repository should be reload or not.
+   * @param function callback Callback which will be called with (err, template)
+   */
+  getTemplate (id, options, callback) {
+    if (typeof options === 'function') {
+      callback = options
+      options = {}
+    }
 
-  if (options.force) {
-    delete this.templates[ids.fullId]
-  }
+    var ids = this.getFullId(id, options)
 
-  if (ids.fullId in this.templates) {
-    return callback(null, this.templates[ids.fullId])
-  }
-
-  var opt = JSON.parse(JSON.stringify(options))
-  opt.templateId = ids.entityId
-  opt.repositoryId = ids.repositoryId
+    if (options.force) {
+      delete this.templates[ids.fullId]
+    }
 
-  this.getRepo(ids.repositoryId, opt, function (err, repoData) {
-    // maybe loaded in the meantime?
     if (ids.fullId in this.templates) {
       return callback(null, this.templates[ids.fullId])
     }
 
-    if (err) {
-      return callback(err, null)
-    }
+    var opt = JSON.parse(JSON.stringify(options))
+    opt.templateId = ids.entityId
+    opt.repositoryId = ids.repositoryId
 
-    if (!repoData.templates || !(ids.entityId in repoData.templates)) {
-      return callback(new Error('template not defined'), null)
-    }
+    this.getRepo(ids.repositoryId, opt, function (err, repoData) {
+      // maybe loaded in the meantime?
+      if (ids.fullId in this.templates) {
+        return callback(null, this.templates[ids.fullId])
+      }
 
-    this.templates[ids.fullId] = OverpassLayer.twig.twig({ data: repoData.templates[ids.entityId], autoescape: true })
+      if (err) {
+        return callback(err, null)
+      }
 
-    callback(null, this.templates[ids.fullId])
-  }.bind(this))
-}
+      if (!repoData.templates || !(ids.entityId in repoData.templates)) {
+        return callback(new Error('template not defined'), null)
+      }
 
-OpenStreetBrowserLoader.prototype.getCategoryFromData = function (id, options, data, callback) {
-  var ids = this.getFullId(id, options)
+      this.templates[ids.fullId] = OverpassLayer.twig.twig({ data: repoData.templates[ids.entityId], autoescape: true })
 
-  if (ids.fullId in this.categories) {
-    return callback(null, this.categories[ids.fullId])
+      callback(null, this.templates[ids.fullId])
+    }.bind(this))
   }
 
-  if (!data.type) {
-    return callback(new Error('no type defined'), null)
-  }
+  getCategoryFromData (id, options, data, callback) {
+    var ids = this.getFullId(id, options)
 
-  if (!(data.type in this.types)) {
-    return callback(new Error('unknown type'), null)
-  }
+    if (ids.fullId in this.categories) {
+      return callback(null, this.categories[ids.fullId])
+    }
 
-  let repository = this.repositories[ids.repositoryId]
+    if (!data.type) {
+      return callback(new Error('no type defined'), null)
+    }
 
-  var opt = JSON.parse(JSON.stringify(options))
-  opt.id = ids.id
-  var layer = new this.types[data.type](opt, data, repository)
+    if (!(data.type in this.types)) {
+      return callback(new Error('unknown type'), null)
+    }
 
-  layer.setMap(this.map)
+    let repository = this.repositories[ids.repositoryId]
 
-  this.categories[ids.fullId] = layer
+    var opt = JSON.parse(JSON.stringify(options))
+    opt.id = ids.id
+    var layer = new this.types[data.type](opt, data, repository)
 
-  if ('load' in layer) {
-    layer.load(function (err) {
-      callback(err, layer)
-    })
-  } else {
-    callback(null, layer)
-  }
-}
+    layer.setMap(this.map)
 
-OpenStreetBrowserLoader.prototype.getFullId = function (id, options) {
-  var result = {}
+    this.categories[ids.fullId] = layer
 
-  if (!id) {
-    return null
+    if ('load' in layer) {
+      layer.load(function (err) {
+        callback(err, layer)
+      })
+    } else {
+      callback(null, layer)
+    }
   }
 
-  let m = id.match(/^(.*)\/([^/]*)/)
-  if (m) {
-    result.id = id
-    result.repositoryId = m[1]
-    result.entityId = m[2]
-  } else if (options.repositoryId && options.repositoryId !== 'default') {
-    result.repositoryId = options.repositoryId
-    result.entityId = id
-    result.id = result.repositoryId + '/' + id
-  } else {
-    result.id = id
-    result.repositoryId = 'default'
-    result.entityId = id
-  }
+  getFullId (id, options) {
+    var result = {}
 
-  result.sublayerId = null
-  m = result.entityId.split(/:/)
-  if (m.length > 1) {
-    result.sublayerId = m[0]
-    result.entityId = m[1]
-  }
+    if (!id) {
+      return null
+    }
 
-  result.fullId = result.repositoryId + '/' + (result.sublayerId ? result.sublayerId + ':' : '') + result.entityId
+    let m = id.match(/^(.*)\/([^/]*)/)
+    if (m) {
+      result.id = id
+      result.repositoryId = m[1]
+      result.entityId = m[2]
+    } else if (options.repositoryId && options.repositoryId !== 'default') {
+      result.repositoryId = options.repositoryId
+      result.entityId = id
+      result.id = result.repositoryId + '/' + id
+    } else {
+      result.id = id
+      result.repositoryId = 'default'
+      result.entityId = id
+    }
 
-  return result
-}
+    result.sublayerId = null
+    m = result.entityId.split(/:/)
+    if (m.length > 1) {
+      result.sublayerId = m[0]
+      result.entityId = m[1]
+    }
 
-OpenStreetBrowserLoader.prototype.forget = function (id) {
-  var ids = this.getFullId(id, options)
+    result.fullId = result.repositoryId + '/' + (result.sublayerId ? result.sublayerId + ':' : '') + result.entityId
 
-  this.categories[ids.fullId].remove()
-  delete this.categories[ids.fullId]
-}
+    return result
+  }
+
+  forget (id) {
+    var ids = this.getFullId(id, options)
 
-OpenStreetBrowserLoader.prototype.registerType = function (type, classObject) {
-  this.types[type] = classObject
+    this.categories[ids.fullId].remove()
+    delete this.categories[ids.fullId]
+  }
+
+  registerType (type, classObject) {
+    this.types[type] = classObject
+  }
 }
 
 module.exports = new OpenStreetBrowserLoader()