jbardon

// Please call 'eatPizza' once you've finished your work
orderPizza(eatPizza);

function orderPizza(callback) {
   // You don't know what's going on here!
   callback(); // <- Hope it's this
}

function eatPizza() {
   console.log('Miam');

jbardon

async function load() {
   let fooPromise = foo();
   let barPromise = bar();
  
   // foo and bar are executed before Promise.all
   let results = await Promise.all([fooPromise, barPromise]);
   console.log(results);
}
load();

jbardon

// ES6 syntax
function load() { 
  return Promise.all([foo(), bar()])
    .then(console.log);
}
load();

// ES7 syntax
async function load() { 
  let a = await foo();

jbardon

const cookPromise = cookPizza();

const packPromise = cookPromise.then(function(pizza) {
    return pack(pizza); // Returns a promise stored in packPromise
});
  
const deliverPromise = packPromise.then(function (packedPizza) { // value from pack(pizza)
    return deliver(packedPizza);
});

jbardon

// Function executed even if there are no then or catch
let promise = Promise.resolve('Pizza');

// Add callbacks later, called depending on the promise status
promise.then(youEatOneSlice);
promise.then(yourFriendEatOneSlice);
promise.then(result => console.log(result)); // 'Pizza'

// Promise is an object (with at least a then function: it's a thenable object)
console.log(promise); // { state: 'fulfilled', value: 'Pizza'}

jbardon

let promise = orderPizza(); // <- No callback 

// Subscribes to the promise
promise.then(eatPizza);     // Fulfilled promise
promise.catch(stillHungry); // Rejected promise

function orderPizza() {
  return Promise.resolve(); // <- returns the promise
}

jbardon

// 1- Call-site issue
const o = { a: 'bar', foo };
callback(o.foo); // undefined

function callback(func){
  func(); // [call-site: callback]
}

// 2- Default binding isn't lexical binding
var a = 'foo';

jbardon

// #2: Implicit binding
const o2 = { a: 'o2', foo };
const o1 = { a: 'o1', o2 };

o1.o2.foo(); // [call-site: o2] 'o2'

// #3: Explicit binding
const o = { a: 'bar' }; 
foo.call(o); // [call-site: o] 'bar'

jbardon

function foo () {
   console.log( this.a );
}

// #1: Default binding
var a = 'bar';

// [call-site: global]
foo(); // 'bar' or undefined (strict mode)

jbardon

var map = new Map();
map.set(x, 'foo');
map.set(y, 'bar');

console.log(map.get(x), map.get(y)); // 'foo', 'bar'

// undefined, undefined
console.log(map.get({ id: 1 }, map.get({ id: 2});