Why is the asnyc/await function not been waited? - next.js

Question

I am doing an Image Upload feature with Cloudinary. I'm providing an array which may contains base64coded or uploaded image which is a url :
[
"https://res.cloudinary.com/\[userName\]/image/upload/v167xxxx4/luxxxfsgasxxxxxx7t9.jpg", "https://res.cloudinary.com/doeejabc9/image/upload/v1675361225/rf6adyht6jfx10vuzjva.jpg",
"data:image/jpeg;base64,/9j/4AAUSkZJRgABAQEBLAEsAA.......", "data:image/jpeg;base64,/9j/4AAUSkZJRgABAQEBLAEsAA......."
]
I'm using this function to upload the "un-uploaded", which returns the all uploaded version:
export async function uploadImage(el: string[]) {
const partition = el.reduce(
(result: string[][], element: string) => {
element.includes("data:image/")
? result[0].push(element)
: result[1].push(element);
return result;
},
[[], []]
);
for (let i = 0; i < partition[0].length; i++) {
const data = new FormData();
data.append("file", partition[0][i]);
data.append("upload_preset", "my_preset_name");
const res = await fetch(
"https://api.cloudinary.com/v1_1/userName/image/upload",
{
method: "POST",
body: data,
}
);
const file = await res.json();
partition[1].push(file.secure_url);
console.log(partition[1]);
}
return partition[1];
}
Then I will use the return value to update the state and call the api to update database:
const uploaded = await uploadImage(el[1])
console.log(uploaded);
setFinalVersionDoc({
...chosenDocument,
[chosenDocument[el[0]]]: uploaded,
});
However, it always updates the useState before the console.log(uploaded). I thought async/await would make sure the value is updated before moving on.
The GitHub repo is attached for better picture. The fragment is under EditModal in the 'component/document' folder:
https://github.com/anthonychan1211/cms
Thanks a lot!
I am hoping to make the upload happen before updating the state.

Answer 1

The function is correct, but you are trying to await the promise inside the callback function of a forEach, but await inside forEach doesn't work.
This doesn't work:
async function handleEdit() {
const entries = Object.entries(chosenDocument);
entries.forEach(async (el) => { // <------ the problem
if (Array.isArray(el[1])) {
const uploaded = await uploadImage(el[1]);
el[1].splice(0, el[1].length, uploaded);
}
});
[...]
}
If you want to have the same behaviour (forEach runs sequentially), you can use a for const of loop instead.
This works (sequentially)
(execution order guaranteed)
async function handleEdit() {
const entries = Object.entries(chosenDocument);
for (const el of entries) {
// await the promises 1,2,...,n in sequence
if (Array.isArray(el[1])) {
const uploaded = await uploadImage(el[1]);
el[1].splice(0, el[1].length, uploaded);
}
}
}
This also works (in parallel)
(execution order not guaranteed)
async function handleEdit() {
const entries = Object.entries(chosenDocument);
await Promise.all(entries.map(async (el) => {
// map returns an array of promises, and await Promise.all() then executes them all at the same time
if (Array.isArray(el[1])) {
const uploaded = await uploadImage(el[1]);
el[1].splice(0, el[1].length, uploaded);
}
}));
[...]
}
If the order in which your files are uploaded doesn't matter, picking the parallel method will be faster/better.