JS Async Always Returns New Promise

A JavaScript async function always returns a new promise, even if you immediately return a promise.

Experimental Setup

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$ node -v  
v8.4.0
$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.3 LTS
Release:	16.04
Codename:	xenial

Experiments

Confirm that a new promise is always generated by an async function

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// test1.js
const promise = new Promise((resolve,reject)=>resolve());
async function test(){
  return promise;
}
console.log(test() !== test());
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$ node test1.js
true

Examine the behavior of the resolve function passed to executor function of a new promise

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// test2.js
const resolvedPromise = new Promise(resolve => resolve('resolved'));
const rejectedPromise = new Promise((_, reject) => reject('rejected'));
function test2(promise){
  return new Promise(resolve => {
    resolve(promise);
  });
}
test2(resolvedPromise).then(v => {
  console.log('resolvedPromise:', v); 
});
test2(rejectedPromise).catch(v => {
   console.log('rejectedPromise:', v);
});
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$ node test2.js 
resolvedPromise: resolved
rejectedPromise: rejected

Take Away

Working with an async function is equivalent to working within the executor of a new promise.

The resolve function, the first argument of the promise executor, behaves the same as the return statement of an async
function.

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function test() {
  return new Promise((resolve,reject) => {
    // resolve === return
    // reject === throw
  }
}

References