How can I use async/await in the Vue 3.0 setup() function using Typescript

(This question has been answered for JavaScript, see below, but this question is specific for TypeScript, which behaves differently)

I'm trying to use async functionality in Vue3.0 using typescript.

Without async this code works nice:

// file: components/HelloWorld.vue

<template>
  <div class="hello">
    <h1>{{ msg }}</h1>
  </div>
</template>

<script lang="ts">
import {defineComponent} from 'vue'

export default defineComponent({
  name: 'HelloWorld',
  props: {
    msg: String,
  },
  async setup() { // <-- this works without 'async'
    const test = 'test'

    // await doSomethingAsynchronous()

    return {
      test,
    }
  },
})
</script>

With async setup() the component "HelloWorld" disappears from the page, and the Firefox console tells me

"Uncaught (in promise) TypeError: node is null (runtime-dom.esm-bundler.js)"

When I change async setup() to setup(), the code works, but then I would not be able to use async/await inside the setup function.

So my question: how do I use async/await inside the setup() function using Typescript?

EDIT:

The answer to this question: why i got blank when use async setup() in Vue3 shows that async setup() does work with JavaScript, so I would expect it to work in TypeScript as well.

Updated 2021-06-29 14:14:34Z by Boussadjra Brahim
Updated 2020-09-29 09:50:45Z by Hendrik Jan

Try to use onMounted hook to manipulate asynchronous call :

 setup() {
    const users = ref([]);
    onMounted(async () => {
      const res = await axios.get("https://jsonplaceholder.typicode.com/users");
      users.value = res.data;
      console.log(res);
    });

    return {
      users,
    };
  },

LIVE DEMO

Updated 2020-09-29 10:02:47Z by Boussadjra Brahim

Another way of doing this:

 const users = ref([]);
 
 (async () => {
   const res = await axios.get("https://jsonplaceholder.typicode.com/users");
   users.value = res.data;
   console.log(res);
 })()

 return {
   users,
 }

And you don't have to wait for it to mount, this is similar to using created() with the options API.

Note: Don't forget to always have a semicolon ";" before the function statement, otherwise, JavaScript would think that the previous statement was supposed to return a function, the following code, for example, would cause a bug "ref([]) is not a function":

const users = ref([]) // No semicolon here

(async () => {

Another way of preventing this bug is to always have the semicolon on the same line of the function definition, the following code also works:

;(async () => {
Updated 2021-09-10 14:06:48Z by
Updated 2021-05-13 19:30:15Z by gustavodacrvi

An alternative is to use the promise chain, the benefit for doing so is that the code is run even before the beforeCreate lifecycle hook:

import { defineComponent, ref } from 'vue'
import { getData } from './api.js'

export default defineComponent({
  setup() {
    const users = ref([])

    getData().then(({ data }) => (users.value = data))

    return {
      users,
    }
  },
})
Updated 2021-09-21 00:49:12Z by
Updated 2021-06-29 09:11:31Z by Wenfang Du