shims for IE8

Gruntfile.js

@@ -121,6 +121,8 @@ module.exports = function (grunt) {
       shims: [
         'lib/shims/array.indexOf.js',
         'lib/shims/array.filter.js',
+        'lib/shims/array.isArray.js',
+        'lib/shims/object.keys.js',
         'lib/shims/weakmap.js'
       ]
     },

lib/shims/array.isArray.js

@@ -0,0 +1,5 @@
+if (!Array.isArray) {
+  Array.isArray = function(arg) {
+    return Object.prototype.toString.call(arg) === '[object Array]';
+  };
+}

lib/shims/object.keys.js

@@ -0,0 +1,42 @@
+// From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
+// License CC-BY-SA v2.5
+if (!Object.keys) {
+  Object.keys = (function() {
+    'use strict';
+    var hasOwnProperty = Object.prototype.hasOwnProperty,
+      hasDontEnumBug = !({ toString: null }).propertyIsEnumerable('toString'),
+      dontEnums = [
+        'toString',
+        'toLocaleString',
+        'valueOf',
+        'hasOwnProperty',
+        'isPrototypeOf',
+        'propertyIsEnumerable',
+        'constructor'
+      ],
+      dontEnumsLength = dontEnums.length;
+
+    return function(obj) {
+      if (typeof obj !== 'object' && (typeof obj !== 'function' || obj === null)) {
+        throw new TypeError('Object.keys called on non-object');
+      }
+
+      var result = [], prop, i;
+
+      for (prop in obj) {
+        if (hasOwnProperty.call(obj, prop)) {
+          result.push(prop);
+        }
+      }
+
+      if (hasDontEnumBug) {
+        for (i = 0; i < dontEnumsLength; i++) {
+          if (hasOwnProperty.call(obj, dontEnums[i])) {
+            result.push(dontEnums[i]);
+          }
+        }
+      }
+      return result;
+    };
+  }());
+}