add KeysByParent function for recursively getting object keys

otto.go

@@ -655,6 +655,25 @@ func (self Object) Keys() []string {
 	return keys
 }
 
+// Get the keys (and those of the parents) for the object, in order of
+// "closest" to "furthest"
+func (self Object) KeysByParent() [][]string {
+	var a [][]string
+
+	for o := self.object; o != nil; o = o.prototype {
+		var l []string
+
+		o.enumerate(false, func(name string) bool {
+			l = append(l, name)
+			return true
+		})
+
+		a = append(a, l)
+	}
+
+	return a
+}
+
 // Class will return the class string of the object.
 //
 // The return value will (generally) be one of:

otto_test.go

@@ -851,6 +851,22 @@ func TestAPI(t *testing.T) {
 	})
 }
 
+func TestObjectKeys(t *testing.T) {
+	tt(t, func() {
+		vm := New()
+		vm.Eval(`var x = Object.create(null); x.a = 1`)
+		vm.Eval(`var y = Object.create(x); y.b = 2`)
+
+		o1, _ := vm.Object("x")
+		is(o1.Keys(), []string{"a"})
+		is(o1.KeysByParent(), [][]string{{"a"}})
+
+		o2, _ := vm.Object("y")
+		is(o2.Keys(), []string{"b"})
+		is(o2.KeysByParent(), [][]string{{"b"}, {"a"}})
+	})
+}
+
 func TestUnicode(t *testing.T) {
 	tt(t, func() {
 		test, _ := test()