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' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

My code is:

this.http.get(`${environment.apiUrl}/...`)
      .subscribe(response => this.downloadFile(response, "application/ms-excel"));

I tried get and map(...) but didn't work.

Details: angular 5.2

references:

import { HttpClient } from '@angular/common/http';
import 'rxjs/add/observable/throw';
import 'rxjs/add/operator/finally';
import 'rxjs/add/operator/map'
import 'rxjs/add/operator/catch';

Content-Type of response:

Content-Type: application/ms-excel

What's wrong?

Answer 1

Blobs are returned with file type from backend. The following function will accept any file type and popup download window:

downloadFile(route: string, filename: string = null): void{

    const baseUrl = 'http://myserver/index.php/api';
    const token = 'my JWT';
    const headers = new HttpHeaders().set('authorization','Bearer '+token);
    this.http.get(baseUrl + route,{headers, responseType: 'blob' as 'json'}).subscribe(
        (response: any) =>{
            let dataType = response.type;
            let binaryData = [];
            binaryData.push(response);
            let downloadLink = document.createElement('a');
            downloadLink.href = window.URL.createObjectURL(new Blob(binaryData, {type: dataType}));
            if (filename)
                downloadLink.setAttribute('download', filename);
            document.body.appendChild(downloadLink);
            downloadLink.click();
        }
    )
}