davidbarral

const { promisify } from "util";

const evenSuccess = (n, onSuccess, onError) => {
  if (n % 2) {
    onError(n);
  } else {
    onSuccess(n);
  }
};

davidbarral

const CUSTOM = Symbol("promisify.custom");

const promisify = fn => {
  if (fn[CUSTOM]) {
    return fn[CUSTOM];
  }

  return (...args) => new Promise((resolve, reject) => {
    fn(...args, (error, value) => {
      if (error) {

davidbarral

const { callbackify } = require("util");

const evenSuccess = n => n % 2 ? Promise.reject("odd") : Promise.resolve("even");

callbackify(evenSuccess)(1, console.log); // "odd"
callbackify(evenSuccess)(2, console.log); // undefined "even"

davidbarral

const curry = fn => (...args) =>
  args.length >= fn.length
    ? fn(...args)
    : (...innerArgs) => fn(...args, ...innerArgs);

davidbarral

const curry = fn => {
  const curryN = (n, fn) => (...args) =>
    args.length >= n
      ? fn(...args)
      : curryN(n - args.length, (...innerArgs) => fn(...args, ...innerArgs));

  return curryN(fn.length, fn);
};

davidbarral

const expect = x => ({
  toBe: y => {
    if (x !== y) {
      throw new Error(`expected ${x} to be ${y}`);
    }
  }
});

const sum4 = curry((a, b, c, d) => a + b + c + d);

davidbarral

const curry = fn => (...args) =>
  args.length >= fn.length
    ? fn(...args)
    : curry((...innerArgs) => fn(...args, ...innerArgs));

davidbarral

expect(sum4(1)(2)(3,4)).toBe(10);
expect(sum4(1)(2)(3)(4)).toBe(10);
expect(sum4(1,2)(3)(4)).toBe(10);

davidbarral

import { curry, __ as _ } from "ramda";

const sum4 = curry((a, b, c, d) => a + b + c + d);

// Currying
sum4(1, 2, 3, 4);
sum4()(1, 2, 3, 4);
sum4(1)(2, 3, 4);
sum4(1)(2)(3, 4);
sum4(1)(2)(3)(4);

davidbarral

// Same as promise.js but with debug messages.
// Just run the code with node promise-debug.js.
// By setting DEBUG to true each promise will output in console some debug info
// There are 13 samples. In terms of debug output is better to focus in one of them at a time.
// You can do that by setting the FOCUS variable (i.e. FOCUS=11)
const DEBUG = false;
const FOCUS = false;

let promiseId = 1;