events: expose Event statics

PR-URL: #34015
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

lib/internal/event_target.js

@@ -125,7 +125,7 @@ class Event {
   get bubbles() { return this.#bubbles; }
   get composed() { return this.#composed; }
   get eventPhase() {
-    return this[kTarget] ? 2 : 0;  // Equivalent to AT_TARGET or NONE
+    return this[kTarget] ? Event.AT_TARGET : Event.NONE;
   }
   get cancelBubble() { return this.#propagationStopped; }
   set cancelBubble(value) {
@@ -136,6 +136,11 @@ class Event {
   stopPropagation() {
     this.#propagationStopped = true;
   }
+
+  static NONE = 0;
+  static CAPTURING_PHASE = 1;
+  static AT_TARGET = 2;
+  static BUBBLING_PHASE = 3;
 }
 
 Object.defineProperty(Event.prototype, SymbolToStringTag, {

test/parallel/test-eventtarget.js

@@ -432,7 +432,6 @@ ok(EventTarget);
   target.removeEventListener('foo', a, { capture: false });
   target.dispatchEvent(new Event('foo'));
 }
-
 {
   const target = new EventTarget();
   strictEqual(target.toString(), '[object EventTarget]');
@@ -464,3 +463,16 @@ ok(EventTarget);
     });
   });
 }
+
+{
+  strictEqual(Event.NONE, 0);
+  strictEqual(Event.CAPTURING_PHASE, 1);
+  strictEqual(Event.AT_TARGET, 2);
+  strictEqual(Event.BUBBLING_PHASE, 3);
+  strictEqual(new Event('foo').eventPhase, Event.NONE);
+  const target = new EventTarget();
+  target.addEventListener('foo', common.mustCall((e) => {
+    strictEqual(e.eventPhase, Event.AT_TARGET);
+  }), { once: true });
+  target.dispatchEvent(new Event('foo'));
+}