File Download (Excel in this case) with Node Server and Angular 2+ App

Angular script:

this._httpService.get(<server url to download a file>
             , {headers: new HttpHeaders({'Content-Type': 'application/octet-stream'}), responseType: 'blob'})
            .subscribe(
                (fileExcel) => {
                    fileExcel;        // this is a blob.
                },
                (error) => {
                    console.log('err');
                }
            );

Node Server Script

res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
res.setHeader('Content-Disposition', `attachment; filename=${options.root}/public/excel/${fileName}`);

res.download(<absolute path with filename>, fileName, options, function (err) {
                            if (err) {
                                if (!res.headersSent) {
                                    res.send('OK');
                                    console.log(res.headersSent);
                                }
                                next(err);
                            } else {
                                console.log('Sent:', fileName);
                            }
                        });