I am trying to code POST REST API request as shown in the above Postman screenshot.

Here is my code:

import { fromFetch } from 'rxjs/fetch';
import { switchMap } from 'rxjs/operators';

interface FetchRequest<TBody> {
  method?: FetchMethod;
  body?: TBody;
  headers?: FetchHeaders;
  isBlobRequest?: boolean;
}

export const request = <TBody extends BodyInit = BodyInit>(
  url: string,
  fetchRequest?: FetchRequest<TBody>,
  contentType: string
) => {
  const { method = 'POST', body, headers } = fetchRequest ?? {};
  const { dispatch } = createStore();
  let request = new Request(`${domainUrl}${url}`, {
    method,
    body: body ? body : null,
    headers: {
      ...headers,
      'Content-type': contentType ,
    },
    credentials: 'include',
  });
  
  return fromFetch(request).pipe(
    switchMap((response: Response) => {
      if (response.status === SUCCESS_CODE) {
        if (isBlobRequest) {
          return response.blob();
        }
        return response.text();
      } else if (response.status === USER_SESSION_EXPIRED_CODE) {
        dispatch(authAsyncActions.setSessionExpired());
        throw response;
      } else {
        // This triggers error-handling and allows us to inspect the entire
        // error response including its status and body
        throw response;
      }
    })
  );
};


const callUploadAPI = (file) => {

      let formData = new FormData();
      formData.append('file', file);
      request(`urlUploadFile`, { method: 'POST', body: formData}, 'application/vnd.ms-excel')

}

In above code I am using fromFetch of "rxjs/fetch" to call the POST REST API and passing "Request" object in fromFetch().

Request interface is inside typescript as per the below screenshot.

Backend is Python flask server and on the backend side in Python code I am using

file = request.files['file']

to get the file which is working when I call the API through Postman but when I call the API through frontend code it is not getting file.

How can I set the Request "Body" type as "form-data" and "KEY" type as File in frontend code?