Add Array.extend prototype

lib/utils/prototypes.js

@@ -53,6 +53,20 @@ Object.defineProperty(Array.prototype, 'map', function (fn, array) {
   return result
 })
 
+Object.defineProperty(Array.prototype, 'extend', {
+  value: function (obj) {
+    if (Array.isArray(obj)) {
+      obj.forEach(function (v) {
+        if (typeof v !== 'undefined') {
+          this.push(v)
+        }
+      }, this)
+    } else {
+      this.push(obj)
+    }
+  }
+})
+
 Object.defineProperty(Object, 'isObject', {
   configurable: true,
   enumerable: false,