update mutation observer handler

1. deep delete from adds set when node was dropped
2. remove node from dropped set when node was added again

src/record/collection.ts

@@ -0,0 +1,41 @@
+/**
+ * Some utils to handle the mutation observer DOM records.
+ * It should be more clear to extend the native data structure
+ * like Set and Map, but currently Typescript does not support
+ * that.
+ */
+
+import { INode } from 'rrweb-snapshot';
+import { removedNodeMutation } from '../types';
+import { mirror } from '../utils';
+
+export function deepDelete(addsSet: Set<Node>, n: Node) {
+  addsSet.delete(n);
+  n.childNodes.forEach(childN => deepDelete(addsSet, childN));
+}
+
+export function isParentRemoved(
+  removes: removedNodeMutation[],
+  n: Node,
+): boolean {
+  const { parentNode } = n;
+  if (!parentNode) {
+    return false;
+  }
+  const parentId = mirror.getId((parentNode as Node) as INode);
+  if (removes.some(r => r.id === parentId)) {
+    return true;
+  }
+  return isParentRemoved(removes, parentNode);
+}
+
+export function isParentDropped(droppedSet: Set<Node>, n: Node): boolean {
+  const { parentNode } = n;
+  if (!parentNode) {
+    return false;
+  }
+  if (droppedSet.has(parentNode)) {
+    return true;
+  }
+  return isParentDropped(droppedSet, parentNode);
+}