read __rrMutationObserver from window

.gitignore

@@ -9,3 +9,5 @@ es
 lib
 
 temp
+
+*.log

package.json

@@ -62,6 +62,6 @@
     "@xstate/fsm": "^1.4.0",
     "fflate": "^0.4.4",
     "mitt": "^1.1.3",
-    "rrweb-snapshot": "^1.0.3"
+    "rrweb-snapshot": "^1.0.4"
   }
 }

src/record/mutation.ts

@@ -112,6 +112,7 @@ function isINode(n: Node | INode): n is INode {
  */
 export default class MutationBuffer {
   private frozen: boolean = false;
+  private locked: boolean = false;
 
   private texts: textCursor[] = [];
   private attributes: attributeCursor[] = [];
@@ -195,7 +196,6 @@ export default class MutationBuffer {
   };
 
   public emit = () => {
-
     if (this.frozen || this.locked) {
       return;
     }

src/record/observer.ts

@@ -44,6 +44,9 @@ import {
 import MutationBuffer from './mutation';
 import { stringify } from './stringify';
 
+type WindowWithStoredMutationObserver = Window & {
+  __rrMutationObserver?: MutationObserver;
+};
 type WindowWithAngularZone = Window & {
   Zone?: {
     __symbol__?: (key: string) => string;
@@ -71,7 +74,17 @@ function initMutationObserver(
     recordCanvas,
     slimDOMOptions,
   );
-  let mutationBufferCtor = window.MutationObserver;
+  let mutationBufferCtor =
+    window.MutationObserver ||
+    /**
+     * Some websites may disable MutationObserver by removing it from the window object.
+     * If someone is using rrweb to build a browser extention or things like it, they
+     * could not change the website's code but can have an opportunity to inject some
+     * code before the website executing its JS logic.
+     * Then they can do this to store the native MutationObserver:
+     * window.__rrMutationObserver = MutationObserver
+     */
+    (window as WindowWithStoredMutationObserver).__rrMutationObserver;
   const angularZoneSymbol = (window as WindowWithAngularZone)?.Zone?.__symbol__?.(
     'MutationObserver',
   );

yarn.lock

@@ -2749,10 +2749,10 @@ rollup@^2.3.3:
   optionalDependencies:
     fsevents "~2.1.2"
 
-rrweb-snapshot@^1.0.1:
-  version "1.0.2"
-  resolved "https://registry.npmjs.org/rrweb-snapshot/-/rrweb-snapshot-1.0.2.tgz#0338c9e00e24e86f8efb56cbdb293def7287f53c"
-  integrity sha512-QtWwK9fqNLn1wn7nupyy/BcTnMfl8rrtG6uQ0pC3xeXskVQ9GXuh/ulEpuzyVIVPszF/AvT4DjfWmwC5K6xusA==
+rrweb-snapshot@^1.0.4:
+  version "1.0.4"
+  resolved "https://registry.yarnpkg.com/rrweb-snapshot/-/rrweb-snapshot-1.0.4.tgz#608acf0f066e4f72213109ee6bfe25d291e7eb0b"
+  integrity sha512-I9oeK+LPeFE8N8MT011gBLEb+3VjnU3TJNHphzqDu5XJLna8bvMx9tkTiyD9MOlVCX80Le/MwSBxoJMpCX9uQA==
 
 run-async@^2.2.0:
   version "2.4.1"