Asynchronous Javascript Promises code stop at "order created", how to fix the issue?

Question

I wanted to convert callback hell to promises.

function createOrder() {
  setTimeout(function() {
    console.log("order created");
      setTimeout(function() {
         console.log("order received");
            setTimeout(function() {
               console.log("preparing food");
                  setTimeout(function() {
                      console.log("order ready");
                          setTimeout(function() {
                             console.log("order delivered");
                          }, 6000)
                   }, 4000)
             }, 5000)
      }, 1000)
   }, 2000)
}

createOrder();

So I did this:

let p = new Promise(function (resolve, reject) {
  setTimeout(() => {
    console.log("order created");

  }, 9000)

})

p.then(function () {
  setTimeout(() => {
    console.log("order received");
  }, 2000);
})

  .then(function () {
    setTimeout(() => {
      console.log("preparing food");
    }, 3000);
  })

  .then(function () {
    setTimeout(() => {
      console.log("order ready");
    }, 4000);
  })

  .then(function () {
    setTimeout(() => {
      console.log("order delivered");
    }, 10000);
  })

But my code stops at "order created". Why's it like that? Please help me fix this issue and mainly understand why it is happening and the fix.

But similar code does work.

function createOrder() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log('Order created')
      resolve()
    }, 9000)
  })
}

createOrder()
  .then(() => {
    setTimeout(() => {
      console.log('Order received')

    }, 3000)
  })
  .then(() => {
    setTimeout(() => {
      console.log('Preparing food')

    }, 5000)
  })
  .then(() => {
    setTimeout(() => {
      console.log('Order Ready')

    }, 4000)
  })
  .then(() => {
    setTimeout(() => {
      console.log('Order delivered')
    }, 6000)
  })

I don't understand the reason why my code should not work but the another code can work properly.

Expected output:

order created

order received

preparing food

order ready

order delivered

Your 'similar code' doesn't work either. It doesn't wait for the other timeouts. — tkausl, Dec 19 '22 at 02:29
@kdqdmmg0 the similar code is working because it calls resolve — coagmano, Dec 19 '22 at 03:20
@coagmano but tkausl says it doesn't work? Is that code correct? — kdqdmmg0, Dec 20 '22 at 04:48

score 0 · Accepted Answer · answered Dec 19 '22 at 02:29

0

You need to call resolve or reject when using Promises. To make this simpler, you can use an async function instead.

const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
(async()=>{
  await sleep(1000);
  console.log("order created");
  await sleep(1000);
  console.log("order received");
  await sleep(1000);
  console.log("preparing food");
  await sleep(1000);
  console.log("order ready");
  await sleep(1000);
  console.log("order delivered");
})();

answered Dec 19 '22 at 02:29

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what does await sleep(1000) does? it waits till 1000ms? – kdqdmmg0 Dec 20 '22 at 04:21
@kdqdmmg0 It waits for 1000 milliseconds. – Unmitigated Dec 20 '22 at 04:23
is the "similar code" correct?@tkausl says it doesn't work. – kdqdmmg0 Dec 20 '22 at 04:48
@kdqdmmg0 Not exactly. Each of the other setTimeouts does not wait for the previous ones. – Unmitigated Dec 20 '22 at 04:50

Asynchronous Javascript Promises code stop at "order created", how to fix the issue?

1 Answers1