Using a setTimeout in a async function

Question

I have a async function that waits for an axios call to complete before proceeding. The problem is that I need to put a timeout on the axios call to half a second so that I don't hit the shopify API call limit.

async function processMatchingSchools(customer_metafield_url) {
  for (const item of customer_metafield_url) {
    await axios.get(item).then((res) => {
      for (key in res.data.metafields) {
        if (res.data.metafields[key].value === schoolName) {
          id_for_each_student.push(shopifyAdmin + "/customers/" + res.data.metafields[key].owner_id + "/metafields.json")
        }
      }
    })
  }
  console.log("Customer metafields to search", id_for_each_student)
  processOwnerIds(id_for_each_student)
}

when I try putting a setTimeout, it calls the setTimeout and moves on before completing the axios calls.

async function processMatchingSchools(customer_metafield_url) {
  for (const item of customer_metafield_url) {
    await setTimeout(function(item) {
      axios.get(item).then((res) => {
        for (key in res.data.metafields) {
          if (res.data.metafields[key].value === schoolName) {
            id_for_each_student.push(shopifyAdmin + "/customers/" + res.data.metafields[key].owner_id + "/metafields.json")
          }
        }
      })
    }, 500)
  }
  console.log("Customer metafields to search", id_for_each_student)
  processOwnerIds(id_for_each_student)
}

Any help?

Well, setTimeout isn't promised based, so trying to await for it is slightly odd. — Taplar, Jul 05 '18 at 22:23

score 41 · Answer 1 · answered Jul 05 '18 at 22:23

41

await only works on promises. You need to wrap setTimeout in a promise:

const waitFor = delay => new Promise(resolve => setTimeout(resolve, delay));

await waitFor(500);

answered Jul 05 '18 at 22:23

SLaks

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Patrick Roberts · Accepted Answer · 2023-05-21T01:10:29.863

setTimeout() doesn't return a Promise, but you can wrap it in one like this. I also cleaned up the rest of your code a little.

async function processMatchingSchools(customer_metafield_url) {
  for (const item of customer_metafield_url) {
    await new Promise(resolve => {
      setTimeout(resolve, 500)
    })

    const { data: { metafields } } = await axios.get(item)

    for (const { value, owner_id } of Object.values(metafields)) {
      if (value === schoolName) {
        id_for_each_student.push(`${shopifyAdmin}/customers/${owner_id}/metafields.json`)
      }
    }
  }

  console.log("Customer metafields to search", id_for_each_student)

  processOwnerIds(id_for_each_student)
}

Thanks everyone for helping me out :P And thank-you Patrick for helping me clean my newbie code. — Matthew Werdean, Jul 05 '18 at 22:58

score 9 · Answer 3 · answered Jul 05 '18 at 22:26

setTimeout does not return a promise so cannot be awaited.

You could create your own promise-based setTimeout and use that.

const setTimeoutPromise = timeout => new Promise(resolve => {        
  setTimeout(resolve, timeout);
});

await setTimeoutPromise(500);

score 6 · Answer 4 · answered Jul 05 '18 at 22:24

6

Create a sleep function that returns a promise that you can use, like so:

const sleep = (milliseconds=500) => new Promise(resolve => setTimeout(resolve, milliseconds))

And to use it in an async function:

(async () => {
  console.log("function invoked...")
  await sleep(500)
  console.log("I got here about 500 milliseconds later")
})()

answered Jul 05 '18 at 22:24

Lance Whatley

2,395
1
13
16

it should be `const sleep = ms => {return new Promise(resolve => setTimeout(resolve, ms));} ` – arielhasidim Sep 29 '21 at 19:50

score 4 · Answer 5 · answered Jul 05 '18 at 22:29

4

You need to to create new promise for example like that

function delay(ms){
 return new Promise(resolve => setTimeout(resolve, ms))
}

And then use it in your code before calling API

...
await delay(500)
await axios.get(item).then((res) => {
...

answered Jul 05 '18 at 22:29

undg

787
4
14

score 3 · Answer 6 · answered Sep 29 '21 at 20:03

I created setTimeout2 function that works the same just as a promise:

const setTimeout2 = (callback, ms) => {
  return new Promise(resolve => setTimeout(() => {
    callback();
    resolve();
  }, ms));
}

So, altogether (noticed the setTimeout2 change):

async function processMatchingSchools(customer_metafield_url) {
  for (const item of customer_metafield_url) {
    await setTimeout2(function(item) {
      axios.get(item).then((res) => {
        for (key in res.data.metafields) {
          if (res.data.metafields[key].value === schoolName) {
            id_for_each_student.push(shopifyAdmin + "/customers/" + res.data.metafields[key].owner_id + "/metafields.json")
          }
        }
      })
    }, 500)
  }
  console.log("Customer metafields to search", id_for_each_student)
  processOwnerIds(id_for_each_student)
}

Using a setTimeout in a async function

6 Answers6

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