async.function.unwrapping.promise.js

let resolve; 

const promise = new Promise(_resolve => {
  resolve = _resolve;
});

async function foo () {
  console.log('start foo');
  // We return promise, but fullfil handler will not be executed until this promise will be resolved
  return promise;
}

console.log('before `foo` invoke');
foo().then(result => console.log('unwrapped promise: ',result));
console.log('after `foo` invoke');

// before `foo` invoke
// start foo
// after `foo` invoke

resolve('some-result');

// unwrapped promise: some-result