Angular: How to download a file from HttpClient?

Question

I need download an excel from my backend, its returned a file.

When I do the request I get the error:

TypeError: You provided \'undefined\' wh

Answer 1

After spending much time searching for a response to this answer: how to download a simple image from my API restful server written in Node.js into an Angular component app, I finally found a beautiful answer in this web Angular HttpClient Blob. Essentially it consist on:

API Node.js restful:

   /* After routing the path you want ..*/
  public getImage( req: Request, res: Response) {

    // Check if file exist...
    if (!req.params.file) {
      return res.status(httpStatus.badRequest).json({
        ok: false,
        msg: 'File param not found.'
      })
    }
    const absfile = path.join(STORE_ROOT_DIR,IMAGES_DIR, req.params.file);

    if (!fs.existsSync(absfile)) {
      return res.status(httpStatus.badRequest).json({
        ok: false,
        msg: 'File name not found on server.'
      })
    }
    res.sendFile(path.resolve(absfile));
  }

Angular 6 tested component service (EmployeeService on my case):

  downloadPhoto( name: string) : Observable {
    const url = environment.api_url + '/storer/employee/image/' + name;

    return this.http.get(url, { responseType: 'blob' })
      .pipe(
        takeWhile( () => this.alive),
        filter ( image => !!image));
  }

Template

Component subscriber and use:

@ViewChild('photo') image: ElementRef;

public LoadPhoto( name: string) {
    this._employeeService.downloadPhoto(name)
          .subscribe( image => {
            const url= window.URL.createObjectURL(image);
            this.image.nativeElement.src= url;
          }, error => {
            console.log('error downloading: ', error);
          })    
}