How to use angular2 http API for tracking upload/download progress

Question

Tho there are many adhoc libraries supporting upload/download progress in angular2, I do not know how to do use native angular2 http api to show progress while doing upload/

Answer 1

As of Angular 4.3.x and beyond versions, it can be achieved using the new HttpClient from @angular/common/http.

Read the Listening to progress events section.

Simple upload example (copied from the section mentioned above):

const req = new HttpRequest('POST', '/upload/file', file, {
  reportProgress: true,
});

http.request(req).subscribe(event => {
  // Via this API, you get access to the raw event stream.
  // Look for upload progress events.
  if (event.type === HttpEventType.UploadProgress) {
    // This is an upload progress event. Compute and show the % done:
    const percentDone = Math.round(100 * event.loaded / event.total);
    console.log(`File is ${percentDone}% uploaded.`);
  } else if (event instanceof HttpResponse) {
    console.log('File is completely uploaded!');
  }
});

And for downloading, it might be something like pretty much the same:

const req = new HttpRequest('GET', '/download/file', {
  reportProgress: true,
});

http.request(req).subscribe(event => {
  // Via this API, you get access to the raw event stream.
  // Look for download progress events.
  if (event.type === HttpEventType.DownloadProgress) {
    // This is an download progress event. Compute and show the % done:
    const percentDone = Math.round(100 * event.loaded / event.total);
    console.log(`File is ${percentDone}% downloaded.`);
  } else if (event instanceof HttpResponse) {
    console.log('File is completely downloaded!');
  }
});

Remember in case that you're monitoring a download, the Content-Length has to be set, otherwise, there's no way to the request to be measured.

Answer 2

I would suggest using the native JavaScript XHR wrapped as an Observable, it's fairly easy to create on your own:

upload(file: File): Observable<string | number> {

    let fd: FormData = new FormData();

    fd.append("file", file);

    let xhr = new XMLHttpRequest;

    return Observable.create(observer => {

        xhr.addEventListener("progress", (progress) => {

            let percentCompleted;

            // Checks if we can really track the progress
            if (progress.lengthComputable) {

                // progress.loaded is a number between 0 and 1, so we'll multiple it by 100
                percentCompleted = Math.round(progress.loaded / progress.total * 100);

                if (percentCompleted < 1) {
                    observer.next(0);
                } else {
                    // Emit the progress percentage
                    observer.next(percentCompleted);
                }
            }
        });

        xhr.addEventListener("load", (e) => {

            if (e.target['status'] !== 200) observer.error(e.target['responseText']);

            else observer.complete(e.target['responseText']);
        });

        xhr.addEventListener("error", (err) => {

            console.log('upload error', err);

            observer.error('Upload error');
        });

        xhr.addEventListener("abort", (abort) => {

            console.log('upload abort', abort);

            observer.error('Transfer aborted by the user');
        });

        xhr.open('POST', 'http://some-dummy-url.com/v1/media/files');

        // Add any headers if necessary
        xhr.setRequestHeader("Authorization", `Bearer rqrwrewrqe`);

        // Send off the file
        xhr.send(fd);

        // This function will get executed once the subscription
        // has been unsubscribed
        return () => xhr.abort()
    });
}

And this is how one would use it:

// file is an instance of File that you need to retrieve from input[type="file"] element
const uploadSubscription = this.upload(file).subscribe(progress => {
    if (typeof progress === Number) {
        console.log("upload progress:", progress);
    }
});

// To abort the upload
// we should check whether the subscription is still active
if (uploadSubscription) uploadSubscription.unsubscribe();