feat: .onmessage, .onmessageerror

src/types.ts

@@ -6,6 +6,8 @@ import { WebSocketBroadcastChannel } from "./web-socket-broadcast-channel.ts";
  */
 export interface BroadcastChannelIsh extends EventTarget {
   readonly name: string;
+  onmessage: ((ev: MessageEvent) => void) | null;
+  onmessageerror: ((ev: Event) => void) | null;
   postMessage(message: unknown): void;
   close(): void;
 }

src/web-socket-broadcast-channel.ts

@@ -32,15 +32,23 @@ const log0: Logger = logger(import.meta.url);
  */
 export class WebSocketBroadcastChannel extends EventTarget
   implements BroadcastChannelIsh {
+  onmessage: ((ev: Event) => void) | null = null;
+  onmessageerror: ((ev: Event) => void) | null = null;
   private readonly log: Logger = log0.sub(WebSocketBroadcastChannel.name);
   private closed = false;
   public readonly name: string;
   readonly url: URL;
   constructor(name: string, url: URL = new URL(DEFAULT_WEBSOCKET_URL)) {
     super();
+    this.log.sub("constructor")(`name: ${s(name)}`);
     this.name = name;
     this.url = url;
-    this.log.sub("constructor")(`name: ${s(name)}`);
+    this.addEventListener("message", (e: Event) => this.onmessage?.(e));
+    this.addEventListener(
+      "messageerror",
+      (e: Event) => this.onmessageerror?.(e),
+    );
+
     registerChannel(this);
   }
   postMessage(message: string): void {