Tips for executing forEach on a promise?

Question

Tips for executing forEach on a promise?

I am currently working with a function that returns a promise of an array:

async function functionReturningPromiseOfUserIDs(): Promise<string[]>

My question is, can I use the forEach method on the array returned by this function?

async function runForEachUser() {
   await functionReturningPromiseOfUserIDs().forEach((userID: string) => {
         return userID; // do stuff with userID
   }
}

When I try to do this in TypeScript, it gives me this error:

Property 'forEach' does not exist on type '() => Promise<string[]>'.ts(2339)

javascript typescript

Answer 1

Answer №1

Are you struggling with writing asynchronous functions in Typescript? Here is a tip to avoid common mistakes:

async function runForEachUser() {
   await functionReturningPromiseOfUserIDs().forEach((userID: string) => {
         return userID;
   });
}

Typescript may mistakenly interpret your code as trying to call .forEach() on the promise itself rather than the value it resolves to. To fix this, try modifying your code like this:

async function runForEachUser() {
   (await functionReturningPromiseOfUserIDs()).forEach((userID: string) => {
         return userID;
   });
}

Remember that .forEach() does not consider the return value of the callback.

Answer 2

Are you struggling with writing asynchronous functions in Typescript? Here is a tip to avoid common mistakes:

async function runForEachUser() {
   await functionReturningPromiseOfUserIDs().forEach((userID: string) => {
         return userID;
   });
}

Typescript may mistakenly interpret your code as trying to call .forEach() on the promise itself rather than the value it resolves to. To fix this, try modifying your code like this:

async function runForEachUser() {
   (await functionReturningPromiseOfUserIDs()).forEach((userID: string) => {
         return userID;
   });
}

Remember that .forEach() does not consider the return value of the callback.

Answer 3

Answer №2

Make sure to wait for the Promise that is returned by calling functionReturningPromiseOfUserIDs(). Update your code to begin with this line:

const userIds = await functionReturningPromiseOfUserIDs();

,

Once you have the array of UserIds stored in userIds, you can easily loop through them using userIds.forEach((id) => {}) and perform any operations you need on each UserId.

Answer 4

Make sure to wait for the Promise that is returned by calling functionReturningPromiseOfUserIDs(). Update your code to begin with this line:

const userIds = await functionReturningPromiseOfUserIDs();

,

Once you have the array of UserIds stored in userIds, you can easily loop through them using userIds.forEach((id) => {}) and perform any operations you need on each UserId.

Tips for executing forEach on a promise?

Answer №1

Answer №2

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