Nested promise resolution method

Question

In the code below when I call func I get back a promise that resolves after 3 seconds which resolves to another promise. The nested promise then resolves to the number 43 after an additional 3 seconds. My question is why the console.log returns res:43 after 6 seconds instead of unresolved promise after 3 seconds. I .then func2 but I never .then otherFunc

async function func(){
  const val = func2().then((other)=>{console.log("res:"+other)})
}

async function func2(){
  return new Promise(resolve => {
    setTimeout(()=>resolve(otherfunc()),3000)

  })
}
async function otherfunc(){
  return  new Promise(resolve => {
    setTimeout(()=>resolve(43),3000)

  })
}

The question is not really clear, can you rephrase please? *"My question is why the console.log returns res:43 after 6 seconds instead of unresolved promise after 3 seconds"* — P.S., Oct 08 '18 at 19:35
Because both func2 and otherFunc wait for 3 seconds: `3*2 = 6` — Kevin Jantzer, Oct 08 '18 at 19:38
When do do `.then()` on a value which is `Promise.resolve(someOtherPromise)`, that one `.then()` will wait for both promises, the original and someOtherPromise. They are chained together. — jfriend00, Oct 08 '18 at 19:46
Yes, that's exactly [what "resolve" means](https://stackoverflow.com/a/29269515/1048572). You can't [fulfill a promise with a promise](https://stackoverflow.com/q/32168194/1048572) — Bergi, Oct 08 '18 at 20:46
Thanks everyone I figured that was what was happening I just didn't realize that .then would wait for all promises in the chain to be resolved. — javajunkie, Oct 17 '18 at 14:46

score 0 · Accepted Answer · answered Oct 08 '18 at 19:40

you resolve func2 with another promise which is otherfunc(), so func2 happens to resolve after 3 seconds, which then calls otherfunc which also resolves after 3 seconds. The result you see at your console.log statement shows 43 because the .then() will wait for all promises to complete.

Nested promise resolution method

1 Answers1