upload-with-epics.js

const uploadDocumentEpic = action$ =>
    action$.ofType(UPLOAD_DOCUMENT).switchMap(action => {
        const {id, data} = action.payload
        const sub = new Subject()
        const requester = Observable.fromPromise(
            axios({
                url: 'https://api.foo.com',
                data: {
                    file: data
                },
                onUploadProgress: progressEvent => {
                    sub.next(progressEvent.loaded * 100 / progressEvent.total)
                }
            })
        )

        return Observable.merge(
            requester.map(() => ({
                type: UPLOAD_COMPLETE,
                id
            })),
            sub.map(progress => ({type: PROGRESS_EVENT, payload: progress}))
        )
    })