ufocoder

function closeWithStatus (response, status, headers) {
  const data = headers || {};
  function end () {
    response.writeHead(status, data);
    response.end();
  }
  return end;
}

function closeWithContent (response, status, headers) {

ufocoder

router.get(url, function (req, res) {
  function handleSuccess (file) {
    res.writeHead(200, { "Content-Type": "application/octet-stream" });
    res.write(file);
    res.end();
  }
  function handleError (err) {
    res.writeHead(404);
    res.end();
  }

ufocoder

function runAsPromised (task, ...params) {
  return new Promise((resolve, reject) =>
    task(...params, higherOrderNodeCallback(resolve, reject))
  );
}

runAsPromised(readFile, filePath)
  .then(convertToContent)
  .then(JSON.stringify)
  .then(closeWithContent(res, 200, jsonHeaders))

ufocoder

export const doSomething = higherOrderNodeCallback(doA, doB);

import doSomething from "./do-something";
fstat("./some-file", doSomething);

ufocoder

function passTest () { /* ... */ }
function failTest () { /* ... */ }

const errorCallback = higherOrderNodeCallback(failTest, passTest);
errorCallback(errorObj, null);

const successCallback = higherOrderNodeCallback(passTest, failTest);
successCallback(null, successObj);

ufocoder

readFile(
  filePath,
  higherOrderNodeCallback(
    closeWithContent(res, 200, headers),
    closeWithStatus(res, 404)
  )
);

ufocoder

let x = 96;
get42(); // 42
get36(); // 36
x = 12;
get18(); // 18
x; // 12

ufocoder

function higherOrderNodeCallback (onSuccess, onError) {
  function nodeCallback (err, thingIWant) {
    if (err) {
      onError(err);
    } else {
      onSuccess(thingIWant);
    }
  }
  return nodeCallback;
}

ufocoder

function multiply (multiplier) {
  return function (x) {
    return x * multiplier;
  };
}

// ES6:
// const multiply = x => y => x * y;

const triple = multiply(3);

ufocoder

function rememberX (x) {
  return function getX () {
    return x;
  };
}

// В ES6 этот же код может быть представлен так:
// const rememberX = x => () => x;

const get42 = rememberX(42);