aherve

asyncGreet () {
  this.someThingAsync()
  .then(this.greet.bind(this))
}

aherve

class Foo {
  constructor (name) {
    this.name = name
  }

  greet () {
    console.log('hello, this is ', this.name)
  }

  someThingAsync () {

aherve

const Greeters = []
for (var i = 0 ; i < 10 ; i++) {
  Greeters.push(function () { return console.log(i) })
}

Greeters[0]() // 10
Greeters[1]() // 10
Greeters[2]() // 10

aherve

typeof {} === 'object'  // true
typeof 'a' === 'string' // true
typeof 1 === number     // true
// But....
typeof [] === 'object'  // true

aherve

// These are ok
'abc' === 'abc' // true
1 === 1         // true

// These are not
[1,2,3] === [1,2,3] // false
{a: 1} === {a: 1}   // false
{} === {}           // false

aherve

let s = "bob"
const replaced = s.replace('b', 'l')
replaced === "lob" // first match only
s === "bob" // original string is remained unchanged

aherve

function demoPromise (userId) {
  return User
    .findById(userId)
    .then(user => Promise.all([user, doSomethingAsync(user)]))
    .then(([user, result]) => finalResult(user, result));
}

aherve

import {sleep} from 'previousExample'

async function slowDouble (i): Promise<number> {
  await sleep(1000) // non-blocking
  return 2 * i
}

async function main () {
  // slowDouble is async, therefore it returns a promise
  const result = await Promise.all([1, 2, 3].map(slowDouble))

aherve

function sleep (ms: number) {
  return new Promise(resolve => {
    setTimeout(resolve, ms)
  })
}

async function main () {
  console.log('hello')
  await sleep(1000) // non-blocking
  console.log('good bye')

aherve

// ----- Old school Promise-style ----- //
function nope (): Promise<never> {
  return Promise.reject('lol no')
}

// ----- Hipster async way ----- //
async function asyncNope (): Promise<never> {
  throw 'lol no'
}