src: add iterator for Object

Refs: nodejs#830

napi-inl.h

@@ -1378,6 +1378,37 @@ inline void Object::AddFinalizer(Finalizer finalizeCallback,
   }
 }
 
+Object::iterator::iterator(Object *object, uint32_t index) {
+  _object = object;
+  _index = index;
+  _keys = object->GetPropertyNames();
+}
+
+Object::iterator Napi::Object::begin() {
+  iterator it(this, 0);
+  return it;
+}
+
+Object::iterator Napi::Object::end() {
+  iterator it(this, GetPropertyNames().Length());
+  return it;
+}
+
+Object::iterator Object::iterator::operator ++() {
+  ++_index;
+  return *this;
+}
+
+bool Object::iterator::operator !=(iterator other) {
+  return _index != other._index;
+}
+
+Value Object::iterator::operator *() {
+  Value key = _keys[_index].Value(); // Don't know how to convert this yet
+  Object object = *_object;
+  return object[key];
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // External class
 ////////////////////////////////////////////////////////////////////////////////

napi.h

@@ -742,6 +742,12 @@ namespace Napi {
     inline void AddFinalizer(Finalizer finalizeCallback,
                              T* data,
                              Hint* finalizeHint);
+
+    class iterator;
+
+    iterator begin();
+
+    iterator end();
   };
 
   template <typename T>
@@ -778,6 +784,24 @@ namespace Napi {
     uint32_t Length() const;
   };
 
+  class Object::iterator {
+  public:
+    iterator(Object *object, uint32_t index);
+
+    iterator operator ++();
+
+    bool operator !=(iterator other);
+
+    Value operator *();
+
+  private:
+    Napi::Object *_object;
+    uint32_t _index;
+    Array _keys;
+
+    friend class Object;
+  };
+
   /// A JavaScript array buffer value.
   class ArrayBuffer : public Object {
   public: