event: cancelBubble is a property

Event#cancelBubble is property (and not a function). Change
Event#cancelBubble to a property and add a test.

PR-URL: #33613
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>

lib/internal/event_target.js

@@ -36,12 +36,13 @@ class Event {
   #cancelable = false;
   #timestamp = perf_hooks.performance.now();
 
-  // Neither of these are currently used in the Node.js implementation
+  // None of these are currently used in the Node.js implementation
   // of EventTarget because there is no concept of bubbling or
   // composition. We preserve their values in Event but they are
   // non-ops and do not carry any semantics in Node.js
   #bubbles = false;
   #composed = false;
+  #propagationStopped = false;
 
 
   constructor(type, options) {
@@ -54,6 +55,7 @@ class Event {
     this.#cancelable = !!cancelable;
     this.#bubbles = !!bubbles;
     this.#composed = !!composed;
+    this.#propagationStopped = false;
     this.#type = String(type);
     // isTrusted is special (LegacyUnforgeable)
     Object.defineProperty(this, 'isTrusted', {
@@ -113,11 +115,14 @@ class Event {
   get eventPhase() {
     return this[kTarget] ? 2 : 0;  // Equivalent to AT_TARGET or NONE
   }
-  cancelBubble() {
-    // Non-op in Node.js. Alias for stopPropagation
+  get cancelBubble() { return this.#propagationStopped; }
+  set cancelBubble(value) {
+    if (value) {
+      this.stopPropagation();
+    }
   }
   stopPropagation() {
-    // Non-op in Node.js
+    this.#propagationStopped = true;
   }
 
   get [Symbol.toStringTag]() { return 'Event'; }

test/parallel/test-eventtarget.js

@@ -36,6 +36,7 @@ ok(EventTarget);
   strictEqual(ev.composed, false);
   strictEqual(ev.isTrusted, false);
   strictEqual(ev.eventPhase, 0);
+  strictEqual(ev.cancelBubble, false);
 
   // Not cancelable
   ev.preventDefault();
@@ -50,6 +51,24 @@ ok(EventTarget);
   const ev = new Event('foo', {}, {});
   strictEqual(ev.type, 'foo');
 }
+{
+const ev = new Event('foo');
+  strictEqual(ev.cancelBubble, false);
+  ev.cancelBubble = true;
+  strictEqual(ev.cancelBubble, true);
+}
+{
+  const ev = new Event('foo');
+  strictEqual(ev.cancelBubble, false);
+  ev.stopPropagation();
+  strictEqual(ev.cancelBubble, true);
+}
+{
+  const ev = new Event('foo');
+  strictEqual(ev.cancelBubble, false);
+  ev.cancelBubble = 'some-truthy-value';
+  strictEqual(ev.cancelBubble, true);
+}
 {
   const ev = new Event('foo', { cancelable: true });
   strictEqual(ev.type, 'foo');