RxJs从FileReader发出的多个可观察对象-收集为数组

import { Observable } from 'rxjs';
import { map, toArray } from 'rxjs/operators';

function readAndCollectFiles(files) {
  return new Observable((subscriber) => {
    const reader = new FileReader();

    Array.from(files).forEach((file) => {
      reader.readAsDataURL(file);

      reader.onload = (event) => {
        subscriber.next(event.target.result);
        subscriber.complete();
      };

      reader.onerror = (error) => {
        subscriber.error(error);
      };
    });
  });
}

const fileInput = document.getElementById('file-input');
const file$ = fromEvent(fileInput, 'change').pipe(
  map((event) => event.target.files),
  switchMap((files) => readAndCollectFiles(files)),
  toArray()
);

file$.subscribe((files) => {
  console.log(files);
});