javascriptAsync race conditionMedium

Loading 3 items returns only one

Time: 0:00

BugFind the bug and fix the code

What it should do

loadAll(ids) loads every id and returns all the results in order. Example: await loadAll([1, 2, 3]) → [10, 20, 30].

What happens instead

await loadAll([1, 2, 3]) gives 10, a single number.

const load = (id) =>
    new Promise((r) => setTimeout(() => r(id * 10), id));

async function loadAll(ids) {
    return await Promise.race(ids.map(load));
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Think & Test Cooldown

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Take a moment to read the bug symptom and trace the code with Run & Check before unlocking Hint 1.

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the async and race conditions pattern

A missing await, results in the wrong order, and updates that overwrite each other under load.

Learn the async and race conditions pattern Step through your own code

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javascriptAsync race conditionMedium

Loading 3 items returns only one

Time: 0:00

BugFind the bug and fix the code

What it should do

loadAll(ids) loads every id and returns all the results in order. Example: await loadAll([1, 2, 3]) → [10, 20, 30].

What happens instead

await loadAll([1, 2, 3]) gives 10, a single number.

const load = (id) =>
    new Promise((r) => setTimeout(() => r(id * 10), id));

async function loadAll(ids) {
    return await Promise.race(ids.map(load));
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Think & Test Cooldown

2:00 remaining

Take a moment to read the bug symptom and trace the code with Run & Check before unlocking Hint 1.

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the async and race conditions pattern

A missing await, results in the wrong order, and updates that overwrite each other under load.

Learn the async and race conditions pattern Step through your own code

Loading 3 items returns only one

What it should do

What happens instead

More async and race conditions to practise

Related errors

Loading 3 items returns only one

What it should do

What happens instead

More async and race conditions to practise

Related errors