async / await
async / awaitcallback hell:
get(function() {
send(function() {
notify(function() {
// sth to do
});
});
});
then:
get()
.then(function () {
return send();
})
.then(function () {
return notify();
});
async / await:
(async function () {
await get();
await send();
await notify();
})();