ericelliott

const x = {
  val: 2
};

const x1 = x => Object.assign({}, x, { val: x.val + 1});

const x2 = x => Object.assign({}, x, { val: x.val * 2});

console.log(x1(x2(x)).val); // 5

ericelliott

// Action creators can be impure.
export const addChat = ({
  // cuid is safer than random uuids/v4 GUIDs
  // see usecuid.org
  id = cuid(),
  msg = '',
  user = 'Anonymous',
  timeStamp = Date.now()
} = {}) => ({
  type: ADD_CHAT,

ericelliott

const defaultState = 0;
const reducer = (state = defaultState, action) => {
  switch (action.type) {
    case 'ADD': return state + action.payload;
    default: return state;
  }
};

ericelliott

const actions = [
  { type: 'ADD', payload: 0 },
  { type: 'ADD', payload: 1 },
  { type: 'ADD', payload: 2 }
];

const total = actions.reduce(reducer, 0); // 3

ericelliott

function* crossBridge() {
  const reply = yield 'What is your favorite color?';
  console.log(reply);
  if (reply !== 'yellow') return 'Wrong!'
  return 'You may pass.';
}

{
  const iter = crossBridge();
  const q = iter.next().value; // Iterator yields question

ericelliott

import test from 'tape';

const before = test;
const after = test;

// beforeEach/afterEach rely on shared state.
// That's a big anti-pattern for testing.

// It's also silly to run something before and after
// ever test -- many of your tests won't need it.

ericelliott

const check = fn => (params = []) => {
  const { required } = fn;
  const missing = required.filter(param => !(param in params));

  if (missing.length) {
    throw new Error(`${ fn.name }() Missing required parameter(s):
    ${ missing.join(', ') }`);
  }

  return fn(params);

ericelliott

const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x);

ericelliott

const getSecret = (secret) => {
  return {
    get: () => secret
  };
};

test('Closure for object privacy.', assert => {
  const msg = '.get() should have access to the closure.';
  const expected = 1;
  const obj = getSecret(1);

ericelliott

import { useState, useEffect, useRef } from 'react';
import Web3 from 'web3';
import Fortmatic from 'fortmatic';

const usePromise = () => {
  const ref = [];
  const container = useRef(ref);

  ref[0] = new Promise((resolve, reject) => {
    ref[1] = resolve;