separate dom binding

src/Util/isParentOf.js

@@ -0,0 +1,18 @@
+
+/**
+ * Check if `parent` is a parent of `child`.
+ *
+ * @param {Type} parent
+ * @param {Type} child
+ * @return {Boolean} Whether `parent` is a parent of `child`.
+ */
+export default function isParentOf (parent, child) {
+  child = child._parent
+  while (child !== null) {
+    if (child === parent) {
+      return true
+    }
+    child = child._parent
+  }
+  return false
+}