example.futures.js

import { encaseP, node, encase, map, chain } from "fluture";

const readFileF = filePath => node(done => fs.readFile(filePath, "utf8", done));

const fetchF = url => encaseP(url => fetch(url));

const jsonParseF = encase(jsonString => JSON.parse(jsonString));

const getPackageDownloads = (npmPackageName, onSuccess, onFailure) => {
  readFileF("package.json")
    .pipe(chain(jsonParseF)) // shorthand for chain(jsonString => jsonParseF(jsonString))
    .pipe(map(package => package.name))
    .pipe(
      chain(packageName => fetchF(`/api/v1/package-metadata/${packageName}`))
    )
    .pipe(map(jsonParseF))
    .pipe(map(response => response.data.metadata.downloadCount))
    .pipe(
      fork(error => onFailure(error), downloadCount => onSuccess(downloadCount))
    );
};