Return Value Happens Before forEach

Question

I am trying to sort names in two different array. but when I need to return the final result, it will just return the values first then do the forEach.

    const available = [];
    const taken = [];

    const names = data.split('\n');

    names.forEach(async (name, i) => {

            (data.success !== undefined) ? (availabe.push(name)) : (taken.push(name));

    });
    return {   //This returns 0 for both
        available: available.length,
        taken: taken.length
    }

By using `async` within `forEach` you make the callback return a Promise. Thus, the code is asynchronous and likely run after the function `return`ed. Do you need it there (e.g. for `data.success`)? — Ryuno-Ki, Feb 06 '20 at 20:12
@AshishModi I am doing an http request for each name to check if it's taken or not — HaMoOoOd25, Feb 06 '20 at 20:16
You didn't include the http request code. Did you remember to `await` the http requests? — Benjamin, Feb 06 '20 at 20:17

score 1 · Answer 1 · answered Feb 06 '20 at 20:22

The issue is that forEach doesn't wait for async code. Check here: https://codeburst.io/javascript-async-await-with-foreach-b6ba62bbf404

Try this instead:

async function f() {
    const available = [];
    const taken = [];

    const names = data.split('\n');

    for (const name of names) {
        // await request...
        (data.success !== undefined) ? (availabe.push(name)) : (taken.push(name));
    }

    return {   //This returns 0 for both
        available: available.length,
        taken: taken.length
    }
}

Then, when you call f(), make sure you await f().

Side note: if you have very many names, this could get very slow. You're waiting for each request to complete before beginning the next one. You'll want to look into requesting all the data at once, either with a different http endpoint, or using something like Promise.all() or the async library.

score -1 · Answer 2 · answered Feb 06 '20 at 20:21

-1

The variable name "available" is misspelled as "availabe" in line 8. Other syntax errors may exist; you might try using something link jslint.com.

answered Feb 06 '20 at 20:21

Mophilly

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Return Value Happens Before forEach

2 Answers2