also.js

// with Babel do-expression-transform <https://babeljs.io/docs/plugins/transform-do-expressions/>
function(lhs, rhs) {
  return do {
    if (lhs) {
      Api.fromJS(lhs)
    } else {
      res.firstField = do {
        if (rhs) {
          List(rhs.map((vt) => SomeClass.fromJS(vt)))
        } else {
          List()
        }
      }
  }
}

this.is.es6.js

// ...
  /**
   * Perform the request by first setting up all the needed options and finally
   * returning the promise.
   */
  async doRequest(preparedRequest) {
    winston.debug(`${preparedRequest.method} ${preparedRequest.url}`)
    const response = await this.axios.request(preparedRequest)

    if (response.status !== 200) {
      throw new Error(`Http request not succesfull (status ${response.status})`, response)
    }

    return response.data
  }
// ...