File Uploads with Angular and Express

app.component-snippet.ts

onFilesDropped(files: NgxFileDropEntry[]): void {
  from(files)
    .pipe(
      mergeMap(selectedFile => {
        const fileEntry = selectedFile.fileEntry as FileSystemFileEntry;
        const observableFactory = bindCallback(fileEntry.file) as any;
        const file$ = observableFactory.call(fileEntry) as Observable<File>;
        return file$
          .pipe(
            switchMap(file => this.uploadFile(file))
          );
      })
    ).subscribe(console.log);
}

private uploadFile(file: File): Observable<HttpEvent<unknown>> {
  const url = 'http://localhost:8080/upload';
  const formData: FormData = new FormData();
  formData.append('file', file, file.name);

  return this.httpClient.post(
    url,
    formData,
    {
      reportProgress: true,
      observe: 'events'
    }
  );
}