Idea of how I have implemented a `goBackTo` saga for react-navigation.

navSaga.js

export const goBackTo = function * goBackTo ({ payload: { routeName } }) {
  const { nav } = yield select()

  let targetIndex

  for (let i = nav.index; i > 0; i--) {
    if (nav.routes[i].routeName === routeName) {
      targetIndex = i + 1
      break
    }
  }

  if (targetIndex) {
    // Index found, let's make sure it's within the array (if it's not, it means the current screen
    // was the screen found with the route name, and the index is therefore the next index (which
    // doesn't exist), and so we literally just need to do nothing).
    if (targetIndex < nav.routes.length) {
      const key = nav.routes[targetIndex].key

      yield put(NavigationActions.back({ key }))
    }
  } else {
    // No index found, so let's just go back one screen
    yield put(NavigationActions.back())
  }
}