Deep Read function in TypeScript

reader.ts

import {promisify, all} from 'bluebird';
import {readdir as _rd, lstat as _ls} from 'fs'
import {flatten} from 'ramda'

let readdir = promisify(_rd)
let lstat = promisify(_ls)

export function reader<T>(path:string, f: (string) => T): Promise<T[]> {

  async function iter(path: string): Promise<T[]> {
    let stat = await lstat(path)

    if(stat.isDirectory()) {
      let paths = await readdir(path)
      let routes = await all(paths.map((file) => {
        return iter(`${path}/${file}`)
      }))
      console.log(routes)
      return flatten(routes)
    }
    else {
      let route: T = f(path)
      return [route];
    }
  }

  return iter(path)

}