How to download an excel file in Angular 8 as an API response

Question

I've an API which returns an excel document as response. The request will be one simple json.

I've searched google and found some code base to download the file and I've used it in my application, but I'm getting some errors and unable to find it out the solution. Below are my code base.

component.ts

import rxjs/Rx;

details = {id: 75,name: "some name"}

this.nameService.getData(this.details).subscribe(response => {
this.downloadFile(response);
})

downloadFile(data: Response) {
  const blob = new Blob([data], { type: '.xlsx' });
  const url= window.URL.createObjectURL(blob);
  window.open(url);
}

nameService.ts

getData(postData) {
  return this.httpService.post('https://localhost:8080/getFile/', postData);
}

httpService.ts

constructor(private http: HttpClient)
post(apiEndpoint: string, request: any) :Observable<any> {
 return this.http.post<any>(apiEndpoint,request);
}

with the above code base I'm getting below two errors and the file is not downloaded.

1. Getting the error :

"Type Response is not assignable to type Blobpart" in creating the Blob(const blob = new Blob([data], { type: '.xlsx' });)

2. If I change the data as any (downloadFile(data: any)) the above error(1) will go but I'm getting an httperror response as 'Syntax error: unexpected token P in json at position 0 at json.parse

Kindly help if anyone finds any solution to the above issues.

Answer 1

While using { responseType: 'blob'} as said by most answers here works, I'd suggest using responseType: 'arraybuffer' instead of blob with observe: 'response'. Your call would then look like this:

this.httpClient.get(resource, {
  headers: this.httpHeaders, // Any custom client side headers like Authorization
  observe: 'response',
  responseType: 'arraybuffer'
});

The advantage of this is two-fold:

1. Arraybuffer is a generic stream of bytes and the Blob object can be created using either a blob or an arraybuffer, using the Content-Type
2. observe: 'response' will also include the response headers that you set at the server in the parsed response.

I use this method to put the filename and the MIME Type of the arraybuffer in the Content-Disposition and Content-Type response headers and then use a generic download service at the client-side.

Also, I would suggest using a File object instead of just the Blob, which gives you the flexibility of giving it a filename like so:

public downloadFile(response: any, fileName?: string) {
    const blob = new Blob([response.body], { type: response.headers.get('content-type') });
    fileName = fileName || response.headers.get('content-disposition').split(';')[0];
    const file = new File([blob], fileName, { type: response.headers.get('content-type') });
    saveAs(file);
}

This will also solve the problem that @knbibin raised about using a custom filename.