diff --git a/common/content/abbreviations.js b/common/content/abbreviations.js
index e264666a..fac98e93 100644
--- a/common/content/abbreviations.js
+++ b/common/content/abbreviations.js
@@ -366,23 +366,21 @@ var Abbreviations = Module("abbreviations", {
                         }
                     ],
                     serialize: function () {
-                        return Ary(abbreviations.userHives)
+                        return abbreviations.userHives
                             .filter(h => h.persist)
-                            .map(hive => [
-                                {
-                                    command: this.name,
-                                    arguments: [abbr.lhs],
-                                    literalArg: abbr.rhs,
-                                    options: {
-                                        "-group": hive.name == "user" ? undefined : hive.name,
-                                        "-javascript": callable(abbr.rhs) ? null : undefined
-                                    }
-                                }
-                                for (abbr of hive.merged)
-                                if (abbr.modesEqual(modes))
-                            ]).
-                            flatten().array;
-                    }
+                            .flatMap(hive =>
+                                hive.merged
+                                    .filter(abbr => abbr.modesEqual(modes))
+                                    .map(abbr => ({
+                                        command: this.name,
+                                        arguments: [abbr.lhs],
+                                        literalArg: abbr.rhs,
+                                        options: {
+                                            "-group": hive.name == "user" ? undefined : hive.name,
+                                            "-javascript": callable(abbr.rhs) ? null : undefined
+                                        }
+                                    })));
+                    },
                 });
 
             commands.add([ch + "una[bbreviate]"],
diff --git a/common/content/bookmarks.js b/common/content/bookmarks.js
index aa7f7f9d..ff1768e6 100644
--- a/common/content/bookmarks.js
+++ b/common/content/bookmarks.js
@@ -436,10 +436,9 @@ var Bookmarks = Module("bookmarks", {
             names: ["-tags", "-T"],
             description: "A comma-separated list of tags",
             completer: function tags(context) {
-                context.generate = () => Ary(b.tags
-                                             for (b of bookmarkcache)
-                                             if (b.tags))
-                                            .flatten().uniq().array;
+                context.generate = () => new RealSet(Array.from(bookmarkcache)
+                                                          .flatMap(b.tags));
+
                 context.keys = { text: identity, description: identity };
             },
             type: CommandOption.LIST
diff --git a/common/content/browser.js b/common/content/browser.js
index 966073c6..100c88f6 100644
--- a/common/content/browser.js
+++ b/common/content/browser.js
@@ -243,12 +243,12 @@ var Browser = Module("browser", XPCOM(Ci.nsISupportsWeakReference, ModuleBase),
             { argCount: "0" });
     },
     mappings: function initMappings(dactyl, modules, window) {
-        let openModes = Ary.toObject([
-            [dactyl.CURRENT_TAB, ""],
-            [dactyl.NEW_TAB, "tab"],
-            [dactyl.NEW_BACKGROUND_TAB, "background tab"],
-            [dactyl.NEW_WINDOW, "win"]
-        ]);
+        let openModes = {
+            [dactyl.CURRENT_TAB]: "",
+            [dactyl.NEW_TAB]: "tab",
+            [dactyl.NEW_BACKGROUND_TAB]: "background tab",
+            [dactyl.NEW_WINDOW]: "win",
+        };
 
         function open(mode, args) {
             if (dactyl.forceTarget in openModes)
diff --git a/common/content/dactyl.js b/common/content/dactyl.js
index 346d659b..fefb8109 100644
--- a/common/content/dactyl.js
+++ b/common/content/dactyl.js
@@ -240,8 +240,8 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
 
         let name = commands.add(params.name, params.description,
             function (args) {
-                let results = Ary(params.iterate(args))
-                    .sort((a, b) => String.localeCompare(a.name, b.name));
+                let results = Array.from(params.iterate(args))
+                                   .sort((a, b) => String.localeCompare(a.name, b.name));
 
                 let filters = args.map(arg => {
                     let re = util.regexp.escape(arg);
@@ -261,22 +261,24 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
                         return seen[this.text] + /*L*/" matching items";
                     };
                     context.ignoreCase = true;
+
                     let seen = {};
-                    context.completions = Ary(keys(item).join(" ").toLowerCase().split(/[()\s]+/)
-                                              for (item of params.iterate(args)))
-                        .flatten()
-                        .map(function (k) {
-                            seen[k] = (seen[k] || 0) + 1;
-                            return k;
-                        }).uniq();
+                    context.completions = new RealSet(
+                        Array.from(params.iterate(args))
+                             .flatMap(item => Object.keys(item).join(" ")
+                                                    .toLowerCase().split(/[()\s]+/))
+                             .map(k => {
+                                 seen[k] = (seen[k] || 0) + 1;
+                                 return k;
+                             }));
                 },
                 options: params.options || []
             });
 
         if (params.index)
             this.indices[params.index] = function* () {
-                let results = Ary((params.iterateIndex || params.iterate).call(params, commands.get(name).newArgs()))
-                        .array.sort((a, b) => String.localeCompare(a.name, b.name));
+                let results = Array.from((params.iterateIndex || params.iterate).call(params, commands.get(name).newArgs()))
+                                   .sort((a, b) => String.localeCompare(a.name, b.name));
 
                 for (let obj of results) {
                     let res = dactyl.generateHelp(obj, null, null, true);
@@ -646,7 +648,6 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
      * Initialize the help system.
      */
     initHelp: function initHelp() {
-        util.dumpStack('INIT HELP');
         if ("noscriptOverlay" in window)
             window.noscriptOverlay.safeAllow("dactyl:", true, false);
 
@@ -1415,11 +1416,13 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
 
                 // FIXME: cleanup
                 cleanupValue: config.cleanups.guioptions ||
-                    "rb" + [k for ([k, v] of iter(groups[1].opts))
-                            if (!Dactyl.isToolbarHidden(document.getElementById(v[1][0])))].join(""),
+                    "rb" + Object.entries(groups[1].opts)
+                                 .filter(([k, v]) => !Dactyl.isToolbarHidden(document.getElementById(v[1][0])))
+                                 .map(([k]) => k)
+                                 .join(""),
 
-                values: Ary(groups).map(g => [[k, v[0]] for ([k, v] of iter(g.opts))])
-                                   .flatten(),
+                values: groups.flatMap(g => Object.entries(g.opts)
+                                                  .map(([k, v]) => [k, v[0]])),
 
                 setter: function (value) {
                     for (let group of groups)
diff --git a/common/content/events.js b/common/content/events.js
index 2eb58227..86391f4e 100644
--- a/common/content/events.js
+++ b/common/content/events.js
@@ -23,10 +23,10 @@ var EventHive = Class("EventHive", Contexts.Hive, {
     },
 
     _events: function _events(event, callback) {
-        if (!isObject(event))
-            var [self, events] = [null, Ary.toObject([[event, callback]])];
+        if (isObject(event))
+            var [self, events] = [event, event[callback || "events"]];
         else
-            [self, events] = [event, event[callback || "events"]];
+            [self, events] = [null, { [event]: callback }];
 
         if (hasOwnProp(events, "input") && !hasOwnProp(events, "dactyl-input"))
             events["dactyl-input"] = events.input;
@@ -1141,7 +1141,7 @@ var Events = Module("events", {
                         return this.value.filter(f => f(buffer.documentURI));
                     });
                     memoize(this, "pass", function () {
-                        return new RealSet(Ary.flatten(this.filters.map(f => f.keys)));
+                        return new RealSet(this.filters.flatMap(f => f.keys));
                     });
                     memoize(this, "commandHive", function hive() {
                         return Hive(this.filters, "command");
diff --git a/common/content/hints.js b/common/content/hints.js
index c2ce1a2b..5a7f71a8 100644
--- a/common/content/hints.js
+++ b/common/content/hints.js
@@ -1379,7 +1379,8 @@ var Hints = Module("hints", {
                 },
                 validator: function (value) {
                     let values = DOM.Event.parse(value).map(DOM.Event.bound.stringify);
-                    return Option.validIf(Ary.uniq(values).length === values.length && values.length > 1,
+
+                    return Option.validIf(new RealSet(values).size === values.length && values.length > 1,
                                           _("option.hintkeys.duplicate"));
                 }
             });
diff --git a/common/content/history.js b/common/content/history.js
index 3bedb20d..39259ad3 100644
--- a/common/content/history.js
+++ b/common/content/history.js
@@ -1,6 +1,6 @@
 // Copyright (c) 2006-2008 by Martin Stubenschrott <stubenschrott@vimperator.org>
 // Copyright (c) 2007-2011 by Doug Kearns <dougkearns@gmail.com>
-// Copyright (c) 2008-2014 Kris Maglione <maglione.k@gmail.com>
+// Copyright (c) 2008-2015 Kris Maglione <maglione.k@gmail.com>
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
@@ -290,7 +290,7 @@ var History = Module("history", {
                         description: "The sort order of the results",
                         completer: function (context) {
                             context.compare = CompletionContext.Sort.unsorted;
-                            return Ary.flatten([
+                            return [
                                 "annotation",
                                 "date",
                                 "date added",
@@ -300,10 +300,10 @@ var History = Module("history", {
                                 "title",
                                 "uri",
                                 "visitcount"
-                            ].map(order => [
-                                  ["+" + order.replace(" ", ""), /*L*/"Sort by " + order + " ascending"],
-                                  ["-" + order.replace(" ", ""), /*L*/"Sort by " + order + " descending"]
-                            ]));
+                            ].flatMap(order => [
+                                ["+" + order.replace(" ", ""), /*L*/"Sort by " + order + " ascending"],
+                                ["-" + order.replace(" ", ""), /*L*/"Sort by " + order + " descending"]
+                            ]);
                         }
                     }
                 ],
diff --git a/common/content/key-processors.js b/common/content/key-processors.js
index 551053a5..ac1bbd44 100644
--- a/common/content/key-processors.js
+++ b/common/content/key-processors.js
@@ -17,7 +17,9 @@ var ProcessorStack = Class("ProcessorStack", {
         events.dbg("STACK " + mode);
 
         let main = { __proto__: mode.main, params: mode.params };
-        this.modes = Ary([mode.params.keyModes, main, mode.main.allBases.slice(1)]).flatten().compact();
+        this.modes = Ary([mode.params.keyModes,
+                          main,
+                          mode.main.allBases.slice(1)]).flatten().compact();
 
         if (builtin)
             hives = hives.filter(h => h.name === "builtin");
diff --git a/common/content/mappings.js b/common/content/mappings.js
index 9e4c7e20..95c4428a 100644
--- a/common/content/mappings.js
+++ b/common/content/mappings.js
@@ -116,7 +116,7 @@ var Map = Class("Map", {
         return this.keys.indexOf(name) >= 0;
     },
 
-    get keys() { return Ary.flatten(this.names.map(mappings.bound.expand)); },
+    get keys() { return this.names.flatMap(mappings.bound.expand); },
 
     /**
      * Execute the action for this mapping.
@@ -404,7 +404,7 @@ var Mappings = Module("mappings", {
     iterate: function* (mode) {
         let seen = new RealSet;
         for (let hive of this.hives.iterValues())
-            for (let map of Ary.iterValues(hive.getStack(mode)))
+            for (let map of hive.getStack(mode))
                 if (!seen.add(map.name))
                     yield map;
     },
@@ -646,26 +646,24 @@ var Mappings = Module("mappings", {
                     if (this.name != "map")
                         return [];
                     else
-                        return Ary(mappings.userHives)
+                        return mappings.userHives
                             .filter(h => h.persist)
-                            .map(hive => [
-                                {
-                                    command: "map",
-                                    options: {
-                                        "-count": map.count ? null : undefined,
-                                        "-description": map.description,
-                                        "-group": hive.name == "user" ? undefined : hive.name,
-                                        "-modes": uniqueModes(map.modes),
-                                        "-silent": map.silent ? null : undefined
-                                    },
-                                    arguments: [map.names[0]],
-                                    literalArg: map.rhs,
-                                    ignoreDefaults: true
-                                }
-                                for (map of userMappings(hive))
-                                if (map.persist)
-                            ])
-                            .flatten().array;
+                            .flatMap(hive =>
+                                Array.from(userMappings(hive))
+                                     .filter(map => map.persist)
+                                     .map(map => ({
+                                         command: "map",
+                                         options: {
+                                             "-count": map.count ? null : undefined,
+                                             "-description": map.description,
+                                             "-group": hive.name == "user" ? undefined : hive.name,
+                                             "-modes": uniqueModes(map.modes),
+                                             "-silent": map.silent ? null : undefined
+                                         },
+                                         arguments: [map.names[0]],
+                                         literalArg: map.rhs,
+                                         ignoreDefaults: true
+                                     })));
                 }
             };
             function* userMappings(hive) {
@@ -731,9 +729,11 @@ var Mappings = Module("mappings", {
                 return Array.concat(value).every(findMode);
             },
             completer: function () {
-                return [[Ary.compact([mode.name.toLowerCase().replace(/_/g, "-"), mode.char]), mode.description]
-                        for (mode of modes.all)
-                        if (!mode.hidden)];
+                return modes.all.filter(mode => !mode.hidden)
+                            .map(
+                    mode => [Ary.compact([mode.name.toLowerCase().replace(/_/g, "-"),
+                                          mode.char]),
+                             mode.description]);
             }
         };
 
diff --git a/common/content/modes.js b/common/content/modes.js
index f6f6e4b2..c3cf2d34 100644
--- a/common/content/modes.js
+++ b/common/content/modes.js
@@ -685,8 +685,10 @@ var Modes = Module("modes", {
             },
 
             get values() {
-                return Ary.toObject([[m.name.toLowerCase(), m.description]
-                                     for (m of modes._modes) if (!m.hidden)]);
+                return Ary.toObject(
+                    modes._modes.filter(mode => !mode.hidden)
+                         .map(mode => [mode.name.toLowerCase(),
+                                       mode.description]));
             }
         };
 
diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index 860eed80..409004b0 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -186,7 +186,6 @@ defineModule("base", {
         "Set",
         "Struct",
         "StructBase",
-        "Symbol",
         "TextEncoder",
         "TextDecoder",
         "Timer",
@@ -217,6 +216,7 @@ defineModule("base", {
         "iterOwnProperties",
         "keys",
         "literal",
+        "loadPolyfill",
         "memoize",
         "module",
         "octal",
@@ -228,6 +228,12 @@ defineModule("base", {
     ]
 });
 
+function loadPolyfill(obj) {
+    JSMLoader.loadSubScript("resource://dactyl/polyfill.jsm",
+                            obj);
+}
+loadPolyfill(this);
+
 this.lazyRequire("cache", ["cache"]);
 this.lazyRequire("config", ["config"]);
 this.lazyRequire("messages", ["_", "Messages"]);
@@ -236,11 +242,6 @@ this.lazyRequire("services", ["services"]);
 this.lazyRequire("storage", ["File"]);
 this.lazyRequire("util", ["FailedAssertion", "util"]);
 
-if (typeof Symbol == "undefined")
-    this.Symbol = {
-        iterator: "@@iterator"
-    };
-
 let literal_ = function literal(comment) {
     if (comment)
         return /^function.*?\/\*([^]*)\*\/(?:\/\* use strict \*\/)\s*\S$/.exec(comment)[1];
@@ -1203,34 +1204,19 @@ for (let name of properties(Class.prototype)) {
 }
 
 var closureHooks = {
-    get: function closure_get(target, prop) {
-        if (hasOwnProp(target._closureCache, prop))
+    get(target, prop) {
+        if (prop in target._closureCache)
             return target._closureCache[prop];
 
         let p = target[prop];
         if (callable(p))
             return target._closureCache[prop] = p.bind(target);
         return p;
-    }
-
-    /*
-    getOwnPropertyNames: function getOwnPropertyNames(target) {
-        return [k for (k in properties(target, true))];
     },
-
-    getOwnPropertyDescriptor: function getOwnPropertyDescriptor(target, prop) {
-        let self = this;
-        return {
-            configurable: false,
-            writable: false,
-            get value() { return self.get(target, prop); }
-        }
-    }
-    */
 };
 
 Class.makeClosure = function makeClosure() {
-    this._closureCache = {};
+    this._closureCache = Object.create(null);
 
     return new Proxy(this, closureHooks);
 };
@@ -1402,7 +1388,7 @@ function Struct(...args) {
 
     const Struct = Class(className || "Struct", StructBase, {
         length: args.length,
-        members: Ary(args).map((v, k) => [v, k]).toObject()
+        members: Ary.toObject(args.map((v, k) => [v, k])),
     });
     args.forEach(function (name, i) {
         Struct.prototype.__defineGetter__(name, function () {
@@ -1617,12 +1603,12 @@ function iter(obj, iface) {
     else if (Symbol.iterator in obj)
         res = obj[Symbol.iterator]();
     else if (isinstance(obj, [Ci.nsIDOMHTMLCollection, Ci.nsIDOMNodeList]))
-        res = Ary.iterItems(obj);
+        res = Array.from(obj).entries();
     else if (ctypes && ctypes.CData && obj instanceof ctypes.CData) {
         while (obj.constructor instanceof ctypes.PointerType)
             obj = obj.contents;
         if (obj.constructor instanceof ctypes.ArrayType)
-            res = Ary.iterItems(obj);
+            res = Array.from(obj).entries();
         else if (obj.constructor instanceof ctypes.StructType)
             res = (function* () {
                 for (let prop of obj.constructor.fields) {
@@ -1664,14 +1650,14 @@ function iter(obj, iface) {
     }
 
     if (res === undefined)
-        res = Iterator(obj)[Symbol.iterator]();
+        res = Object.entries(obj).values();
 
     return Iter(res);
 }
 update(iter, {
-    toArray: function toArray(iter) {
-        return Ary(iter).array;
-    },
+    toArray: deprecated("Array.from", function toArray(iter) {
+        return Array.from(iter);
+    }),
 
     // See Ary.prototype for API docs.
     toObject: function toObject(iter) {
@@ -1939,10 +1925,10 @@ var Ary = Class("Ary", Array, {
      * @param {Array} ary
      * @returns {Iterator(Object)}
      */
-    iterValues: function* iterValues(ary) {
+    iterValues: deprecated("Array#values", function* iterValues(ary) {
         for (let i = 0; i < ary.length; i++)
             yield ary[i];
-    },
+    }),
 
     /**
      * Returns an Iterator for an array's indices and values.
@@ -1950,11 +1936,11 @@ var Ary = Class("Ary", Array, {
      * @param {Array} ary
      * @returns {Iterator([{number}, {Object}])}
      */
-    iterItems: function* iterItems(ary) {
+    iterItems: deprecated("Array#entries", function* iterItems(ary) {
         let length = ary.length;
         for (let i = 0; i < length; i++)
             yield [i, ary[i]];
-    },
+    }),
 
     /**
      * Returns the nth member of the given array that matches the
diff --git a/common/modules/bookmarkcache.jsm b/common/modules/bookmarkcache.jsm
index f495a8e9..dcbcb301 100644
--- a/common/modules/bookmarkcache.jsm
+++ b/common/modules/bookmarkcache.jsm
@@ -94,9 +94,12 @@ var BookmarkCache = Module("BookmarkCache", XPCOM(Ci.nsINavBookmarkObserver), {
     bookmarks: Class.Memoize(function () { return this.load(); }),
 
     keywords: Class.Memoize(function () {
-        return Ary.toObject([[b.keyword, b]
-                             for (b of this)
-                             if (b.keyword)]);
+        let res = {};
+        for (let bookmark of this)
+            if (bookmark.keyword)
+                res[bookmark.keyword] = res;
+
+        return res;
     }),
 
     rootFolders: ["toolbarFolder", "bookmarksMenuFolder", "unfiledBookmarksFolder"]
diff --git a/common/modules/buffer.jsm b/common/modules/buffer.jsm
index 6190d28f..72e09314 100644
--- a/common/modules/buffer.jsm
+++ b/common/modules/buffer.jsm
@@ -58,8 +58,8 @@ var Buffer = Module("Buffer", {
      *     buffer. Only returns style sheets for the 'screen' media type.
      */
     get alternateStyleSheets() {
-        let stylesheets = Ary.flatten(
-            this.allFrames().map(w => Array.slice(w.document.styleSheets)));
+        let stylesheets = this.allFrames()
+                              .flatMap(w => w.document.styleSheets);
 
         return stylesheets.filter(
             s => /^(screen|all|)$/i.test(s.media.mediaText) && !/^\s*$/.test(s.title)
@@ -415,11 +415,12 @@ var Buffer = Module("Buffer", {
      * Returns a list of all frames in the given window or current buffer.
      */
     allFrames: function allFrames(win=this.win, focusedFirst) {
-        let frames = iter(util.iterFrames(win)).toArray();
+        let frames = Array.from(util.iterFrames(win));
 
-        if (focusedFirst)
-            return frames.filter(f => f === this.focusedFrame).concat(
-                   frames.filter(f => f !== this.focusedFrame));
+        if (focusedFirst) {
+            let focused = this.focusedFrame;
+            return frames.sort((a, b) => (b === focused) - (a === focused));
+        }
 
         return frames;
     },
@@ -2415,8 +2416,10 @@ var Buffer = Module("Buffer", {
 
                     let frames = buffer.allFrames(undefined, true);
 
-                    let elements = Ary.flatten(frames.map(win => [m for (m of DOM.XPath(xpath, win.document))]))
-                                      .filter(function (elem) {
+                    let elements = Array.from(frames)
+                                        .flatMap(win => DOM.XPath(xpath, win.document))
+                                        .filter(elem => {
+
                         if (isinstance(elem, [Ci.nsIDOMHTMLFrameElement,
                                               Ci.nsIDOMHTMLIFrameElement]))
                             return Editor.getEditor(elem.contentWindow);
@@ -2428,9 +2431,11 @@ var Buffer = Module("Buffer", {
 
                         let style = elem.style;
                         let rect = elem.rect;
+
                         return elem.isVisible &&
-                            (elem[0] instanceof Ci.nsIDOMXULTextBoxElement || style.MozUserFocus != "ignore") &&
-                            rect.width && rect.height;
+                               (elem[0] instanceof Ci.nsIDOMXULTextBoxElement ||
+                                style.MozUserFocus != "ignore") &&
+                               rect.width && rect.height;
                     });
 
                     dactyl.assert(elements.length > 0);
diff --git a/common/modules/commands.jsm b/common/modules/commands.jsm
index 24035957..96f8f1af 100644
--- a/common/modules/commands.jsm
+++ b/common/modules/commands.jsm
@@ -251,7 +251,7 @@ var Command = Class("Command", {
 
     /** @property {[string]} All of this command's long and short names. */
     names: Class.Memoize(function () {
-        return this.names = Ary.flatten(this.parsedSpecs);
+        return this.parsedSpecs.flatMap();
     }),
 
     /** @property {string} This command's description, as shown in :listcommands */
@@ -330,9 +330,9 @@ var Command = Class("Command", {
     _options: [],
 
     optionMap: Class.Memoize(function () {
-        return Ary(this.options)
-                   .map(opt => opt.names.map(name => [name, opt]))
-                   .flatten().toObject();
+        return Ary.toObject(
+            Array.from(this.options)
+                 .flatMap(opt => opt.names.map(name => [name, opt])));
     }),
 
     newArgs: function newArgs(base) {
@@ -456,7 +456,7 @@ var Command = Class("Command", {
      *  @returns {Array}
      */
     parseSpecs: function parseSpecs(specs) {
-        return specs.map(function (spec) {
+        return specs.map(spec => {
             let [, head, tail] = /([^[]+)(?:\[(.*)])?/.exec(spec);
             return tail ? [head + tail, head] : [head];
         });
@@ -498,8 +498,9 @@ var Ex = Module("Ex", {
         args = Array.slice(args);
 
         let res = cmd.newArgs({ context: this.context });
+
         if (isObject(args[0]))
-            for (let [k, v] of iter(args.shift()))
+            for (let [k, v] of Object.entries(args.shift()))
                 if (k == "!")
                     res.bang = v;
                 else if (k == "#")
@@ -515,8 +516,9 @@ var Ex = Module("Ex", {
                     res.explicitOpts[opt.names[0]] = val;
                 }
 
-        for (let [i, val] of Ary.iterItems(args))
+        for (let [i, val] of args.entries())
             res[i] = String(val);
+
         return res;
     },
 
@@ -593,7 +595,9 @@ var CommandHive = Class("CommandHive", Contexts.Hive, {
         if (this.cached)
             this.modules.initDependencies("commands");
         this.cached = false;
-        return Ary.iterValues(this._list.sort((a, b) => a.name > b.name));
+
+        return this._list.sort((a, b) => String.localeCompare(a.name, b.name))
+                   .values();
     },
 
     /** @property {string} The last executed Ex command line. */
@@ -623,7 +627,7 @@ var CommandHive = Class("CommandHive", Contexts.Hive, {
         extra.hive = this;
         extra.parsedSpecs = Command.parseSpecs(specs);
 
-        let names = Ary.flatten(extra.parsedSpecs);
+        let names = extra.parsedSpecs.flatMap();
         let name = names[0];
 
         if (this.name != "builtin") {
@@ -934,10 +938,10 @@ var Commands = Module("commands", {
 
         let defaults = {};
         if (args.ignoreDefaults)
-            defaults = Ary(this.options).map(opt => [opt.names[0], opt.default])
-                                        .toObject();
+            defaults = Ary.toObject(Array.from(this.options,
+                                               opt => [opt.names[0], opt.default]));
 
-        for (let [opt, val] of iter(args.options || {})) {
+        for (let [opt, val] of Object.entries(args.options || {})) {
             if (val === undefined)
                 continue;
             if (val != null && defaults[opt] === val)
@@ -1788,28 +1792,32 @@ var Commands = Module("commands", {
                 literal: 1,
 
                 serialize: function () {
-                    return Ary(commands.userHives)
+                    return commands.userHives
                         .filter(h => h.persist)
-                        .map(hive => [
-                            {
+                        .flatMap(hive =>
+                            Array.from(hive)
+                                 .filter(cmd => cmd.persist)
+                                 .map(cmd =>
+                            ({
                                 command: this.name,
                                 bang: true,
-                                options: iter([v, typeof cmd[k] == "boolean" ? null : cmd[k]]
-                                            // FIXME: this map is expressed multiple times
-                                            for ([k, v] of iter({
-                                                argCount: "-nargs",
-                                                bang: "-bang",
-                                                count: "-count",
-                                                description: "-description"
-                                            }))
-                                            if (cmd[k])).toObject(),
+                                options: Ary.toObject(
+                                    Object.entries({
+                                        argCount: "-nargs",
+                                        bang: "-bang",
+                                        count: "-count",
+                                        description: "-description",
+                                    })
+                                    .filter(([k, v]) => cmd[k])
+                                    .map(([k, v]) => [
+                                        v,
+                                        typeof cmd[k] == "boolean" ? null : cmd[k]
+                                    ])),
                                 arguments: [cmd.name],
                                 literalArg: cmd.action,
                                 ignoreDefaults: true
-                            }
-                            for (cmd of hive) if (cmd.persist)
-                        ])
-                        .flatten().array;
+                            }))
+                        );
                 }
             });
 
diff --git a/common/modules/completion.jsm b/common/modules/completion.jsm
index 6bb12d1f..27a6b998 100644
--- a/common/modules/completion.jsm
+++ b/common/modules/completion.jsm
@@ -284,17 +284,17 @@ var CompletionContext = Class("CompletionContext", {
                 get longestSubstring() { return self.longestAllSubstring; },
 
                 get items() {
-                    return Ary.flatten(self.activeContexts.map(function m(context) {
+                    return self.activeContexts.flatMap(context => {
                         let prefix = self.value.substring(minStart, context.offset);
 
-                        return context.items.map(function m(item) {
+                        return context.items.map(item => {
                             return {
                                 text: prefix + item.text,
                                 result: prefix + item.result,
                                 __proto__: item
                             };
                         });
-                    }));
+                    });
                 }
             });
 
@@ -323,24 +323,23 @@ var CompletionContext = Class("CompletionContext", {
          * Possibly.
          */
         let substrings = lists.reduce(
-            function r(res, list) {
-                return res.filter(function f(str) {
-                    return list.some(function s_(s) {
-                        return s.substr(0, str.length) == str;
-                    });
+            (res, list) => {
+                return res.filter(str => {
+                    return list.some(s => s.substr(0, str.length) == str);
                 });
             },
             lists.pop());
 
         if (!substrings) // FIXME: How is this undefined?
             return [];
+
         return Ary.uniq(Array.slice(substrings));
     },
     // Temporary
     get longestAllSubstring() {
         return this.allSubstrings.reduce(function r(a, b) {
-            return a.length > b.length ? a : b, "";
-        });
+            return a.length > b.length ? a : b;
+        }, "");
     },
 
     get caret() { return this._caret - this.offset; },
diff --git a/common/modules/config.jsm b/common/modules/config.jsm
index aa8d842e..c73cd0e5 100644
--- a/common/modules/config.jsm
+++ b/common/modules/config.jsm
@@ -235,20 +235,19 @@ var ConfigBase = Class("ConfigBase", {
 
         let uri = "resource://dactyl-locale/";
         let jar = io.isJarURL(uri);
+        let res;
         if (jar) {
             let prefix = getDir(jar.JAREntry);
-            var res = iter(s.slice(prefix.length).replace(/\/.*/, "")
-                           for (s of io.listJar(jar.JARFile, prefix)))
-                        .toArray();
+            res = Array.from(io.listJar(jar.JARFile, prefix),
+                             s => slice(prefix.length).replace(/\/.*/, ""));
         }
         else {
-            res = Ary(f.leafName
-                      // Fails on FF3: for (f of util.getFile(uri).iterDirectory())
-                      for (f of util.getFile(uri).readDirectory())
-                      if (f.isDirectory())).array;
+            res = Array.from(util.getFile(uri).readDirectory())
+                       .filter(f => f.isDirectory())
+                       .map(f => f.leafName);
         }
 
-        let exists = function exists(pkg) {
+        let exists = pkg => {
             return services["resource:"].hasSubstitution("dactyl-locale-" + pkg);
         };
 
@@ -265,9 +264,14 @@ var ConfigBase = Class("ConfigBase", {
      * @returns {string}
      */
     bestLocale: function (list) {
-        return values([this.appLocale, this.appLocale.replace(/-.*/, ""),
-                       "en", "en-US", list[0]])
-            .find(bind("has", new RealSet(list)));
+        let candidates =  [this.appLocale,
+                           this.appLocale.replace(/-.*/, ""),
+                           "en",
+                           "en-US",
+                           list[0]];
+
+        list = new RealSet(list);
+        return candidates.find(locale => list.has(locale));
     },
 
     /**
diff --git a/common/modules/dom.jsm b/common/modules/dom.jsm
index 58aedc89..eccfb85a 100644
--- a/common/modules/dom.jsm
+++ b/common/modules/dom.jsm
@@ -723,17 +723,17 @@ var DOM = Class("DOM", {
         return this[0].getAttributeNS(ns, key);
     },
 
-    css: update(function css(key, val) {
+    css: update(function css(props, val = undefined) {
         if (val !== undefined)
-            key = Ary.toObject([[key, val]]);
+            props = { [props]: val };
 
-        if (isObject(key))
-            return this.each(function (elem) {
-                for (let [k, v] of iter(key))
+        if (isObject(props))
+            return this.each(elem => {
+                for (let [k, v] of Object.entries(props))
                     elem.style[css.property(k)] = v;
             });
 
-        return this[0].style[css.property(key)];
+        return this[0].style[css.property(props)];
     }, {
         name: function (property) {
             return property.replace(/[A-Z]/g, m0 => "-" + m0.toLowerCase());
@@ -895,13 +895,13 @@ var DOM = Class("DOM", {
         if (isObject(event))
             capture = listener;
         else
-            event = Ary.toObject([[event, listener]]);
+            event = { [event]: listener };
 
-        for (let [evt, callback] of iter(event))
+        for (let [evt, callback] of Object.entries(event))
             event[evt] = util.wrapCallback(callback, true);
 
-        return this.each(function (elem) {
-            for (let [evt, callback] of iter(event))
+        return this.each(elem => {
+            for (let [evt, callback] of Object.entries(event))
                 elem.addEventListener(evt, callback, capture);
         });
     },
@@ -909,30 +909,31 @@ var DOM = Class("DOM", {
         if (isObject(event))
             capture = listener;
         else
-            event = Ary.toObject([[event, listener]]);
+            event = { [event]: listener };
 
-        return this.each(function (elem) {
-            for (let [k, v] of iter(event))
-                elem.removeEventListener(k, v.wrapper || v, capture);
+        return this.each(elem => {
+            for (let [event, callback] of Object.entries(event))
+                elem.removeEventListener(event, callback.wrapper || v, capture);
         });
     },
     once: function once(event, listener, capture) {
         if (isObject(event))
             capture = listener;
         else
-            event = Ary.toObject([[event, listener]]);
+            event = { [event]: listener };
 
         for (let pair of iter(event)) {
             let [evt, callback] = pair;
             event[evt] = util.wrapCallback(function wrapper(event) {
                 this.removeEventListener(evt, wrapper.wrapper, capture);
+
                 return callback.apply(this, arguments);
             }, true);
         }
 
-        return this.each(function (elem) {
-            for (let [k, v] of iter(event))
-                elem.addEventListener(k, v, capture);
+        return this.each(elem => {
+            for (let [event, callback] of Object.entries(event))
+                elem.addEventListener(event, callback, capture);
         });
     },
 
@@ -940,6 +941,7 @@ var DOM = Class("DOM", {
         this.canceled = false;
         return this.each(function (elem) {
             let evt = DOM.Event(this.document, event, params, elem);
+
             if (!DOM.Event.dispatch(elem, evt, extraProps))
                 this.canceled = true;
         }, this);
@@ -1231,7 +1233,7 @@ var DOM = Class("DOM", {
          */
         parse: function parse(input, unknownOk=true) {
             if (isArray(input))
-                return Ary.flatten(input.map(k => this.parse(k, unknownOk)));
+                return input.flatMap(k => this.parse(k, unknownOk));
 
             let out = [];
             for (let match of util.regexp.iterate(/<.*?>?>|[^<]|<(?!.*>)/g, input)) {
@@ -1971,11 +1973,11 @@ var DOM = Class("DOM", {
      * @returns {string}
      */
     makeXPath: function makeXPath(nodes) {
-        return Ary(nodes).map(util.debrace).flatten()
-                         .map(node => /^[a-z]+:/.test(node) ? node
-                                                            : [node, "xhtml:" + node])
-                         .flatten()
-                         .map(node => "//" + node).join(" | ");
+        return nodes.flatMap(util.debrace)
+                    .flatMap(node => /^[a-z]+:/.test(node) ? node
+                                                           : [node, "xhtml:" + node])
+                    .map(node => "//" + node)
+                    .join(" | ");
     },
 
     namespaces: {
diff --git a/common/modules/help.jsm b/common/modules/help.jsm
index a34a3cfb..c2a2dffd 100644
--- a/common/modules/help.jsm
+++ b/common/modules/help.jsm
@@ -27,16 +27,16 @@ var HelpBuilder = Class("HelpBuilder", {
 
             // Scrape the list of help files from all.xml
             this.tags["all"] = this.tags["all.xml"] = "all";
-            let files = this.findHelpFile("all").map(doc =>
-                    [f.value for (f of DOM.XPath("//dactyl:include/@href", doc))]);
+            let files = this.findHelpFile("all").flatMap(
+                doc => Array.from(DOM.XPath("//dactyl:include/@href", doc),
+                                  f => f.value));
 
             // Scrape the tags from the rest of the help files.
-            Ary.flatten(files).forEach(function (file) {
+            for (let file of files) {
                 this.tags[file + ".xml"] = file;
-                this.findHelpFile(file).forEach(function (doc) {
+                for (let doc of this.findHelpFile(file))
                     this.addTags(file, doc);
-                }, this);
-            }, this);
+            }
         }
         finally {
             delete help._data;
@@ -129,10 +129,12 @@ var Help = Module("Help", {
                 | (?: ^ [^\S\n]* \n) +
             `), "gmxy");
 
-            let betas = util.regexp(/\[((?:b|rc)\d)\]/, "gx");
+            let matchBetas = util.regexp(/\[((?:b|rc)\d)\]/, "gx");
 
-            let beta = Ary(betas.iterate(NEWS))
-                        .map(m => m[1]).uniq().slice(-1)[0];
+            let betas = Array.from(betas.iterate(NEWS),
+                                   match => match[1]);
+
+            let beta = betas.sort().pop();
 
             function rec(text, level, li) {
                 let res = [];
@@ -154,7 +156,9 @@ var Help = Module("Help", {
                     else if (match.par) {
                         let [, par, tags] = /([^]*?)\s*((?:\[[^\]]+\])*)\n*$/.exec(match.par);
                         let t = tags;
-                        tags = Ary(betas.iterate(tags)).map(m => m[1]);
+
+                        tags = Array.from(matchBetas.iterate(tags),
+                                          match => match[1]);
 
                         let group = !tags.length               ? "" :
                                     !tags.some(t => t == beta) ? "HelpNewsOld" : "HelpNewsNew";
diff --git a/common/modules/highlight.jsm b/common/modules/highlight.jsm
index 8c7693fa..25ebca4b 100644
--- a/common/modules/highlight.jsm
+++ b/common/modules/highlight.jsm
@@ -456,13 +456,13 @@ var Highlights = Module("Highlight", {
             context.keys = { text: f => f.leafName.replace(extRe, ""),
                              description: ".parent.path" };
             context.completions =
-                Ary.flatten(
-                      io.getRuntimeDirectories("colors").map(
-                          dir => dir.readDirectory()
-                                    .filter(file => extRe.test(file.leafName))))
-                   .concat([
-                      { leafName: "default", parent: { path: /*L*/"Revert to builtin colorscheme" } }
-                   ]);
+                io.getRuntimeDirectories("colors")
+                  .flatMap(dir => dir.readDirectory()
+                                     .filter(file => extRe.test(file.leafName)))
+                  .concat([
+                      { leafName: "default",
+                        parent: { path: /*L*/"Revert to builtin colorscheme" } }
+                  ]);
 
         };
 
diff --git a/common/modules/io.jsm b/common/modules/io.jsm
index b2c8a243..dfeaee06 100644
--- a/common/modules/io.jsm
+++ b/common/modules/io.jsm
@@ -589,11 +589,13 @@ var IO = Module("io", {
      *     otherwise, the return value of *func*.
      */
     withTempFiles: function withTempFiles(func, self, checked, ext, label) {
-        let args = Ary(util.range(0, func.length))
-                    .map(bind("createTempFile", this, ext, label)).array;
+        let args = Array.from(util.range(0, func.length),
+                              () => this.createTempFile(ext, label));
+
         try {
             if (!args.every(identity))
                 return false;
+
             var res = func.apply(self || this, args);
         }
         finally {
@@ -679,11 +681,10 @@ var IO = Module("io", {
                 dactyl.assert(!file.exists() || args.bang, _("io.exists", JSON.stringify(file.path)));
 
                 // TODO: Use a set/specifiable list here:
-                let lines = [cmd.serialize().map(commands.commandToString, cmd)
-                             for (cmd of commands.iterator())
-                             if (cmd.serialize)];
-
-                lines = Ary.flatten(lines);
+                let lines = Array.from(commands.iterator())
+                                 .filter(cmd => cmd.serialize)
+                                 .flatMap(cmd => cmd.serialize()
+                                                    .map(commands.commandToString, cmd));
 
                 lines.unshift('"' + config.version + "\n");
                 lines.push("\n\" vim: set ft=" + config.name + ":");
@@ -840,7 +841,7 @@ let &cpo = s:cpo_save
 unlet s:cpo_save
 
 " vim: tw=130 et ts=8 sts=4 sw=4:
-`;//}}}
+`;//}}} "
 
                 const { options } = modules;
 
@@ -876,15 +877,21 @@ unlet s:cpo_save
                     appname: config.appName,
                     fileext: config.fileExtension,
                     maintainer: "Doug Kearns <dougkearns@gmail.com>",
+
                     autocommands: wrap("syn keyword " + config.name + "AutoEvent ",
-                                       keys(config.autocommands)),
+                                       Object.keys(config.autocommands)),
+
                     commands: wrap("syn keyword " + config.name + "Command ",
-                                  Ary(c.specs for (c of commands.iterator())).flatten()),
+                                   Array.from(commands.iterator()).flatMap(cmd => cmd.specs)),
+
                     options: wrap("syn keyword " + config.name + "Option ",
-                                  Ary(o.names for (o of options) if (o.type != "boolean")).flatten()),
+                                  Array.from(options).filter(opt => opt.type != "boolean")
+                                                     .flatMap(opt => opt.names)),
+
                     toggleoptions: wrap("let s:toggleOptions = [",
-                                        Ary(o.realNames for (o of options) if (o.type == "boolean"))
-                                            .flatten().map(JSON.stringify),
+                                        Array.from(options).filter(opt => opt.type == "boolean")
+                                                           .flatMap(opt => opt.realNames)
+                                                           .map(JSON.stringify),
                                         ", ") + "]"
                 }; //}}}
 
@@ -1103,16 +1110,14 @@ unlet s:cpo_save
             context.title = ["Shell Command", "Path"];
             context.generate = () => {
                 let dirNames = services.environment.get("PATH").split(config.OS.pathListSep);
-                let commands = [];
 
-                for (let dirName of dirNames) {
+                return dirNames.flatMap(dirName => {
                     let dir = io.File(dirName);
                     if (dir.exists() && dir.isDirectory())
-                        commands.push([[file.leafName, dir.path] for (file of iter(dir.directoryEntries))
-                                       if (file.isFile() && file.isExecutable())]);
-                }
-
-                return Ary.flatten(commands);
+                        return Array.from(dir.directoryEntries)
+                                    .filter(file => file.isFile() && file.isExecutable())
+                                    .map(file => [file.leafName, dir.path])
+                });
             };
         };
 
diff --git a/common/modules/javascript.jsm b/common/modules/javascript.jsm
index 77d6c2e1..387aed55 100644
--- a/common/modules/javascript.jsm
+++ b/common/modules/javascript.jsm
@@ -110,9 +110,10 @@ var JavaScript = Module("javascript", {
         if (isPrototypeOf.call(this.toplevel, obj) && !toplevel)
             return [];
 
-        let completions = [k for (k of this.iter(obj, toplevel))];
+        let completions = Array.from(this.iter(obj, toplevel));
         if (obj === this.modules) // Hack.
-            completions = Ary.uniq(completions.concat([k for (k of this.iter(this.modules.jsmodules, toplevel))]));
+            completions = [...new RealSet([...completions,
+                                           ...this.iter(this.modules.jsmodules, toplevel)])];
         return completions;
     },
 
@@ -640,7 +641,9 @@ var JavaScript = Module("javascript", {
      * enumerable by any standard method.
      */
     globalNames: Class.Memoize(function () {
-        return Ary.uniq([
+        let interfaces = Object.keys(Ci);
+
+        let names = new RealSet([
             "Array", "ArrayBuffer", "AttributeName", "Audio", "Boolean", "Components",
             "CSSFontFaceStyleDecl", "CSSGroupRuleRuleList", "CSSNameSpaceRule",
             "CSSRGBColor", "CSSRect", "ComputedCSSStyleDeclaration", "Date", "Error",
@@ -655,11 +658,14 @@ var JavaScript = Module("javascript", {
             "XMLList", "XMLSerializer", "XPCNativeWrapper",
             "XULControllers", "constructor", "decodeURI", "decodeURIComponent",
             "encodeURI", "encodeURIComponent", "escape", "eval", "isFinite", "isNaN",
-            "isXMLName", "parseFloat", "parseInt", "undefined", "unescape", "uneval"
-        ].concat([k.substr(6) for (k of keys(Ci)) if (/^nsIDOM/.test(k))])
-         .concat([k.substr(3) for (k of keys(Ci)) if (/^nsI/.test(k))])
-         .concat(this.magicalNames)
-         .filter(k => k in this.window));
+            "isXMLName", "parseFloat", "parseInt", "undefined", "unescape", "uneval",
+
+            ...interfaces.filter(key => /^nsIDOM/.test(key)).map(key => k.substr(6)),
+            ...interfaces.filter(key => /^nsI/.test(key)).map(key => k.substr(3)),
+            ...this.magicalNames,
+        ]);
+
+        return [...names].filter(key => key in this.window);
     })
 }, {
     EVAL_TMP: "__dactyl_eval_tmp",
diff --git a/common/modules/main.jsm b/common/modules/main.jsm
index 8784dd85..2b6ae6ee 100644
--- a/common/modules/main.jsm
+++ b/common/modules/main.jsm
@@ -104,6 +104,8 @@ var Modules = function Modules(window) {
                                                  wantXrays: true,
                                                  metadata: { addonID: config.addon.id } });
 
+        loadPolyfill(sandbox);
+
         // Hack:
         // sandbox.Object = jsmodules.Object;
         sandbox.File = global.File;
diff --git a/common/modules/messages.jsm b/common/modules/messages.jsm
index 01bb4469..866d7e52 100644
--- a/common/modules/messages.jsm
+++ b/common/modules/messages.jsm
@@ -1,4 +1,4 @@
-// Copyright (c) 2011-2014 Kris Maglione <maglione.k@gmail.com>
+// Copyright (c) 2011-2015 Kris Maglione <maglione.k@gmail.com>
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
@@ -40,25 +40,24 @@ var Messages = Module("messages", {
     },
 
     bundles: Class.Memoize(function () {
-        let urls = [
+        let urls = new RealSet([
             JSMLoader.getTarget("dactyl://locale/"),
             JSMLoader.getTarget("dactyl://locale-local/"),
             "resource://dactyl-locale/en-US/",
             "resource://dactyl-locale-local/en-US/"
-        ].map(url => url + this.name + ".properties");
+        ].map(url => url + this.name + ".properties"));
 
-        return Ary.uniq(urls, true)
-                  .map(services.stringBundle.createBundle)
-                  .filter(bundle => {
-                      try {
-                          bundle.getSimpleEnumeration();
-                          return true;
-                      }
-                      catch (e) {
-                          return false;
-                      }
-                  });
-   }),
+        return Array.from(urls, services.stringBundle.createBundle)
+                    .filter(bundle => {
+                        try {
+                            bundle.getSimpleEnumeration();
+                            return true;
+                        }
+                        catch (e) {
+                            return false;
+                        }
+                    });
+    }),
 
     iterate: function* () {
         let seen = new RealSet;
@@ -111,12 +110,16 @@ var Messages = Module("messages", {
         file = io.File(file);
 
         function properties(base, iter_, prop="description") {
-            return iter(function* _properties() {
+            return Array.from(function* _properties() {
                 function key(...args) {
-                    return [base, obj.identifier || obj.name].concat(args).join(".").replace(/[\\:=]/g, "\\$&");
+                    return [base,
+                            obj.identifier || obj.name,
+                            ...args]
+                           .join(".")
+                           .replace(/[\\:=]/g, "\\$&");
                 }
 
-                for (var obj of iter_) {
+                for (let obj of iter_) {
                     if (!obj.hive || obj.hive.name !== "user") {
                         yield key(prop) + " = " + obj[prop];
 
@@ -135,20 +138,22 @@ var Messages = Module("messages", {
                             yield key("deprecated") + " = " + obj.deprecated;
                     }
                 }
-            }()).toArray();
+            }());
         }
 
-        file.write(
-            Ary(commands.allHives.map(h => properties("command", h)))
-                        .concat(modes.all.map(m =>
-                            properties("map", values(mappings.builtin.getStack(m)
-                                                             .filter(map => map.modes[0] == m)))))
-                        .concat(properties("mode", values(modes.all.filter(m => !m.hidden))))
-                        .concat(properties("option", options))
-                        .concat(properties("hintmode", values(hints.modes), "prompt"))
-                        .concat(properties("pageinfo", values(Buffer.pageInfo), "title"))
-                        .concat(properties("sanitizeitem", values(sanitizer.itemMap)))
-                .flatten().uniq().join("\n"));
+        let allMessages = [
+            ...commands.allHives.map(h => properties("command", h)),
+            ...modes.all.flatMap(m =>
+                properties("map", values(mappings.builtin.getStack(m)
+                                                 .filter(map => map.modes[0] == m)))),
+            ...properties("mode", values(modes.all.filter(m => !m.hidden))),
+            ...properties("option", options),
+            ...properties("hintmode", values(hints.modes), "prompt"),
+            ...properties("pageinfo", values(Buffer.pageInfo), "title"),
+            ...properties("sanitizeitem", values(sanitizer.itemMap)),
+        ];
+
+        file.write(allMessages.join("\n"));
     }
 }, {
     Localized: Class("Localized", Class.Property, {
diff --git a/common/modules/options.jsm b/common/modules/options.jsm
index 63ddec28..359962d5 100644
--- a/common/modules/options.jsm
+++ b/common/modules/options.jsm
@@ -611,7 +611,7 @@ var Option = Class("Option", {
         list: function list(value, parse) {
             let prev = null;
             return Ary.compact(Option.splitList(value, true)
-                                       .map(function (v) {
+                                     .map(v => {
                 let [count, filter, quote] = Commands.parseArg(v, /:/, true);
 
                 let val = v.substr(count + 1);
@@ -624,7 +624,7 @@ var Option = Class("Option", {
                     util.assert(prev, _("error.syntaxError"), false);
                     prev.result += "," + v;
                 }
-            }, this));
+            }));
         },
     },
 
@@ -886,7 +886,7 @@ var Option = Class("Option", {
 
 update(BooleanOption.prototype, {
     names: Class.Memoize(function () {
-        return Ary.flatten([[name, "no" + name] for (name of this.realNames)]);
+        return this.realNames.flatMap(name => [name, "no" + name]);
     })
 });
 
@@ -1504,7 +1504,7 @@ var Options = Module("options", {
                     bang: true,
                     completer: setCompleter,
                     domains: function domains(args) {
-                        return Ary.flatten(args.map(function (spec) {
+                        return args.flatMap(spec => {
                             try {
                                 let opt = modules.options.parseOpt(spec);
                                 if (opt.option && opt.option.domains)
@@ -1514,17 +1514,17 @@ var Options = Module("options", {
                                 util.reportError(e);
                             }
                             return [];
-                        }));
+                        });
                     },
                     keepQuotes: true,
-                    privateData: function privateData(args) {
-                        return args.some(function (spec) {
-                            let opt = modules.options.parseOpt(spec);
-                            return opt.option && opt.option.privateData &&
-                                   (!callable(opt.option.privateData) ||
-                                   opt.option.privateData(opt.values));
-                        });
-                    }
+                    privateData: args => args.some(spec => {
+                        let opt = modules.options.parseOpt(spec);
+
+                        return (opt.option &&
+                                opt.option.privateData &&
+                                (!callable(opt.option.privateData) ||
+                                 opt.option.privateData(opt.values)));
+                    }),
                 }, params.extra || {}));
         });
 
diff --git a/common/modules/overlay.jsm b/common/modules/overlay.jsm
index bd42c1c1..0a2ba60e 100644
--- a/common/modules/overlay.jsm
+++ b/common/modules/overlay.jsm
@@ -71,10 +71,10 @@ var Overlay = Module("Overlay", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReferen
         let doc = target.ownerDocument || target.document || target;
         let listeners = this.getData(doc, "listeners");
 
-        if (!isObject(event))
-            var [self, events] = [null, Ary.toObject([[event, callback]])];
+        if (isObject(event))
+            var [self, events] = [event, event[callback || "events"]];
         else
-            [self, events] = [event, event[callback || "events"]];
+            [self, events] = [null, { [event]: callback }];
 
         for (let [event, callback] of iter(events)) {
             let args = [Cu.getWeakReference(target),
diff --git a/common/modules/polyfill.jsm b/common/modules/polyfill.jsm
new file mode 100644
index 00000000..097b9262
--- /dev/null
+++ b/common/modules/polyfill.jsm
@@ -0,0 +1,70 @@
+// Copyright (c) 2015 Kris Maglione <maglione.k@gmail.com>
+//
+// This work is licensed for reuse under an MIT license. Details are
+// given in the LICENSE.txt file included with this file.
+"use strict";
+
+// Implementations for some ES6 and ES7 features that aren't in Firefox
+// mainline yet.
+
+{
+    // This is similar to the same-named function in self-hosted JS, but
+    // somewhat less efficient.
+    //
+    // It helps dodge some of the pitfalls of using the `call` method of the
+    // function you're intending to call, which might have been replaced,
+    // and can fail for other reasons (on CPOWs, most notably).
+    let callFunction = Function.call.bind(Function.call);
+
+    let identity = x => x;
+
+    if (!Object.entries)
+        Object.entries = function (obj) {
+            let result = [];
+
+            for (let key of Object.keys(obj)) {
+                // The check is necessary, since keys may be removed during
+                // iteration.
+                if (key in obj)
+                    result.push([key, obj[val]]);
+            }
+
+            return result;
+        };
+
+    if (!Object.values)
+        Object.values = function (obj) {
+            let result = [];
+
+            for (let key of Object.keys(obj)) {
+                // The check is necessary, since keys may be removed during
+                // iteration.
+                if (key in obj)
+                    result.push(obj[val]);
+            }
+
+            return result;
+        };
+
+    if (!Array.prototype.flatMap)
+        Array.prototype.flatMap = function (fn = identity, self = null) {
+            let result = [];
+
+            for (let [i, value] of Array.prototype.entries.call(this)) {
+                let res = callFunction(fn, self, value, i);
+
+                if (isObject(res) && Symbol.iterator in res)
+                    result.push(...res);
+                else if (res !== undefined)
+                    result.push(res);
+            }
+
+            return result;
+        };
+
+    if (!Array.prototype.values)
+        Array.prototype.values = function* () {
+            for (let [i, value] of this.entries())
+                yield value;
+        };
+}
diff --git a/common/modules/styles.jsm b/common/modules/styles.jsm
index aaba1097..e7ef5a20 100644
--- a/common/modules/styles.jsm
+++ b/common/modules/styles.jsm
@@ -125,9 +125,9 @@ var Hive = Class("Hive", {
     },
 
     get sites() {
-        return Ary(this.sheets).map(s => s.sites)
-                               .flatten()
-                               .uniq().array;
+        let sites = this.sheets.flatMap(s => s.sites);
+
+        return [...new RealSet(sites)];
     },
 
     /**
@@ -557,6 +557,7 @@ var Styles = Module("Styles", {
                     ' (?:[^\\']|\\.)* (?:'|$)
                 )
             `, "gx", this);
+            // " Vim.
         },
 
         get token() {
@@ -617,7 +618,11 @@ var Styles = Module("Styles", {
                 let [filter, css] = args;
 
                 if (!css)
-                    styles.list(window.content, filter ? filter.split(",") : null, args["-name"], args.explicitOpts["-group"] ? [args["-group"]] : null);
+                    styles.list(window.content,
+                                filter ? filter.split(",") : null,
+                                args["-name"],
+                                args.explicitOpts["-group"] ? [args["-group"]]
+                                                            : null);
                 else {
                     util.assert(args["-group"].modifiable && args["-group"].hive.modifiable,
                                 _("group.cantChangeBuiltin", _("style.styles")));
@@ -660,9 +665,9 @@ var Styles = Module("Styles", {
                     { names: ["-nopersist", "-N"], description: "Do not save this style to an auto-generated RC file" }
                 ],
                 serialize: function () {
-                    return Ary(styles.hives)
+                    return styles.hives
                         .filter(hive => hive.persist)
-                        .map(hive =>
+                        .flatMap(hive =>
                              hive.sheets.filter(style => style.persist)
                                  .sort((a, b) => String.localeCompare(a.name || "",
                                                                       b.name || ""))
@@ -674,8 +679,7 @@ var Styles = Module("Styles", {
                                         "-group": hive.name == "user" ? undefined : hive.name,
                                         "-name": style.name || undefined
                                     }
-                                })))
-                        .flatten().array;
+                                })));
                 }
             });
 
diff --git a/common/modules/util.jsm b/common/modules/util.jsm
index 7f4bbda3..4099f220 100644
--- a/common/modules/util.jsm
+++ b/common/modules/util.jsm
@@ -1778,9 +1778,9 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
      * @returns {Generator(nsIDOMWindow)}
      */
     iterFrames: function* iterFrames(win) {
-            yield win;
-            for (let i = 0; i < win.frames.length; i++)
-                yield* iterFrames(win.frames[i]);
+        yield win;
+        for (let i = 0; i < win.frames.length; i++)
+            yield* iterFrames(win.frames[i]);
     },
 
     /**