Write simple asynchronous code with JavaScript generators

generator.js

// 1. Use JavaScript (ES6) generators to pause function execution
function* createLogger() {
	console.log('Start')
	yield
	console.log('Second block')
	yield
	console.log('Third block')
	yield
	console.log('End')
}

const logger = createLogger()
logger.next()
logger.next()
logger.next()
logger.next()

// 2. Send messages to and from JavaScript (ES6) generators
function* createHello() {
	const word = yield
	console.log(word)
}

const hello = createHello()
console.log(hello.next())
console.log(hello.next('Max'))

// 3. Error handling in JavaScript (ES6) generators
function* createHello() {
	try {
		const word = yield
		console.log(`Hello ${word}`)
	} catch (err) {
		console.log('ERROR', err)
	}
}

const hello = createHello()
hello.next()
hello.throw('Something went wrong.')

// 4. Iterate over JavaScript (ES6) generators
function* createCounter() {
	yield 1
	yield 2
	yield 3
	yield 4
}

const counter = createCounter()
for (let i of counter) {
	console.log(i)
}

// 5. Delegate JavaScript (ES6) generator iteration control
function* create3To4Counter() {
	yield 3
	return 4
}

function* createCounter() {
	yield 1
	yield 2
	const four = yield* create3To4Counter()
	console.log(four)
	yield 5
}

for (let i of createCounter()) {
	console.log(i)
}

// 6. Use JavaScript (ES6) generators with Promises to handle async flows
function* createQuoteFetcher() {
  const response = yield fetch('http://api.forismatic.com/api/1.0/?method=getQuote&lang=en&format=json')
  const quote = yield response.json()
  return `${quote.quoteText} —${quote.quoteAuthor}`
}

const coroutine = (gen) => {
  const generator = gen()

  const handle = (result) => {
    if (result.done) return Promise.resolve(result.value)
    return Promise.resolve(result.value)
      .then(res => handle(generator.next(res)))
	}

  return handle(generator.next())
}

const quoteFetcher = coroutine(createQuoteFetcher)
quoteFetcher.then(quote => console.log(quote))