when is onuploadprogresscalled axios

1const config = {
2    onUploadProgress: progressEvent => console.log(progressEvent.loaded)
3}

1let response = await axios({
2  method: 'post',
3  url: imageUploadUrl,
4  data: {
5    connectorId,
6    data
7  },
8  onUploadProgress: (progressEvent) => {
9    const { loaded, total } = progressEvent;
10    dispatch(updateImageUploadProgress(loaded, total));
11  },
12  cancelToken: new CancelToken(token => {
13    cancelAxiosRequest = token;
14  })
15});
16