ES6-ify some things. Still a long way to go...

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;
+        };
+}