Angular -Download file from a output-stream as a BLOB

HttpClientService.ts

  getFiles(url) {
    const headers = new HttpHeaders(
      {
        'X-Auth-Token': this.util.accessToken
      });
      return this._http.get(this.baseUrl + url, { headers: headers, responseType: "blob",  observe: 'response'});
  }

//observe : response -- means it will return complete response with header and body.

resource.ts

constructor(private http: HttpClientService,
    private util: Util, private sharedService: SharedService) { }

ngOnInit() {
this.downloadFile();
  }



  downloadFile() {
    this.http.getFiles(AppUrl.getResources).subscribe((response: any) => {
      this.sharedService.onSuccess('', '', () => {
        this.util.downloadFile(response);
      });
    }, error => {
      this.sharedService.onError(error);

    })
  }

util.ts

  downloadFile(response) {
    let header_content = response.headers.get('content-disposition');
    let file = header_content.split('=')[1];
    file = file.substring(1, file.length - 1);
    let extension = file.split('.')[1].toLowerCase();
    // It is necessary to create a new blob object with mime-type explicitly set
    // otherwise only Chrome works like it should
    var newBlob = new Blob([response.body], { type: this.createFileType(extension) })

    // IE doesn't allow using a blob object directly as link href
    // instead it is necessary to use msSaveOrOpenBlob
    if (window.navigator && window.navigator.msSaveOrOpenBlob) {
      window.navigator.msSaveOrOpenBlob(newBlob);
      return;
    }

    // For other browsers: 
    // Create a link pointing to the ObjectURL containing the blob.
    const data = window.URL.createObjectURL(newBlob);
    var link = document.createElement('a');
    link.href = data;
    link.download = file;
    link.click();
    setTimeout(() => {
      // For Firefox it is necessary to delay revoking the ObjectURL
      window.URL.revokeObjectURL(data);
    }, 400)
  }

  createFileType(e): string {
    let fileType: string = "";
    if (e == 'pdf' || e == 'csv') {
      fileType = `application/${e}`;
    }
    else if (e == 'jpeg' || e == 'jpg' || e == 'png') {
      fileType = `image/${e}`;
    }
    else if (e == 'txt') {
      fileType = 'text/plain';
    }

    else if (e == 'ppt' || e == 'pot' || e == 'pps' || e == 'ppa') {
      fileType = 'application/vnd.ms-powerpoint';
    }
    else if (e == 'pptx') {
      fileType = 'application/vnd.openxmlformats-officedocument.presentationml.presentation';
    }
    else if (e == 'doc' || e == 'dot') {
      fileType = 'application/msword';
    }
    else if (e == 'docx') {
      fileType = 'application/vnd.openxmlformats-officedocument.wordprocessingml.document';
    }
    else if (e == 'xls' || e == 'xlt' || e == 'xla') {
      fileType = 'application/vnd.ms-excel';
    }
    else if (e == 'xlsx') {
      fileType = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet';
    }

    return fileType;
  }