Why is an array of documents taken from an async function empty even if I loaded it?

Question

I load an array of documents using an async function. If I print in the console the array.length this value result 0, but if I print the array I can see all the values, and they seems correctly loaded.

const array = [];

async function getArray() {
  const arraySnaps = await getDocs(collection(db, "CollectionName"));

  for(var i = 0; i < arraySnaps.docs.length; i++){
      arrayList[i] = arraySnaps.docs[i].data();
  }

  return array;
}
getArray();
console.log(array.length);
console.log(array);

This is a problem because I can not use the values in other parts of code, because the array result empty.

If you need I can also post the two logs.

Does this answer your question? [Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference](https://stackoverflow.com/questions/23667086/why-is-my-variable-unaltered-after-i-modify-it-inside-of-a-function-asynchron) — Yoshi, Dec 06 '21 at 10:48

TheTisiboth · Accepted Answer · 2021-12-06T11:08:17.793

You have to use the useEffect hook, to be able to fetch your data once your component has been mounted, and store this data in the state of your component:

  export default function App() {
    const [array, setArray] = useState([]);
    useEffect(() => {
      async function getArray() {
        // Fetch asynchronously the data
        const arraySnaps= await getDocs(collection(db, "CollectionName"))
        // Get the needed info from them
        const array = arraySnaps.docs.map(doc => doc.data())
        // Store it in the local state of our component
        setArray(array);
      }
      // This function is called one time, once the component is mounted
      getArray();
    }, []);
    // Initialy, array is an empty array, and once we fetched the data, the component will be rerended with the fetched array
    console.log(array.length);
    console.log(array);
}

Why is an array of documents taken from an async function empty even if I loaded it?

1 Answers1