Adding onClose callback to AsyncIter

src/asynciter.ts

@@ -7,17 +7,22 @@ interface IAsyncIteratorMessage<T> {
    close: true | undefined;
 }
 export default class AsyncIteratorFromCB<T> implements AsyncIterable<T> {
-   private onData = new Observable<IAsyncIteratorMessage<T>>();
+   #onClose: (() => void)[] = [];
+   #onData = new Observable<IAsyncIteratorMessage<T>>();
    constructor() {}
 
+   public onClose(callback: () => void) {
+      this.#onClose.push(callback);
+   }
+
    public getCallback() {
       return (error: Error | undefined, data: T | undefined) => {
-         this.onData.send({ error, data, close: undefined });
+         this.#onData.send({ error, data, close: undefined });
       };
    }
 
    public send(data: T) {
-      this.onData.send({
+      this.#onData.send({
          error: undefined,
          data,
          close: undefined,
@@ -25,18 +30,19 @@ export default class AsyncIteratorFromCB<T> implements AsyncIterable<T> {
    }
 
    public close() {
-      this.onData.send({
+      this.#onData.send({
          close: true,
          data: undefined,
          error: undefined,
       });
-      this.onData.close();
+      this.#onData.close();
+      this.#onClose.forEach((cb) => cb());
    }
 
    [Symbol.asyncIterator]() {
       const queue: IAsyncIteratorMessage<T>[] = [];
       const signal = new Signal();
-      this.onData.subscribe((data) => {
+      this.#onData.subscribe((data) => {
          queue.push(data);
          signal.sendSignal();
       });