javascriptLogic errorEasy

Flattening nested category list leaves inner arrays unflattened

Time: 0:00

BugFind the bug and fix the code

What it should do

flatten_nested_categories(categories) flattens a deeply nested array of category names into a single flat array. Example: flatten_nested_categories([1, [2, [3, 4]]]) → [1, 2, 3, 4].

What happens instead

flatten_nested_categories([1, [2, [3, 4]]]) returns [1, 2, [3, 4]] with inner array still unflattened.

function flatten_nested_categories(categories) {
  return categories.flat();
}

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

⏱️0:00

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Hint 2

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Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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javascriptLogic errorEasy

Flattening nested category list leaves inner arrays unflattened

Time: 0:00

BugFind the bug and fix the code

What it should do

flatten_nested_categories(categories) flattens a deeply nested array of category names into a single flat array. Example: flatten_nested_categories([1, [2, [3, 4]]]) → [1, 2, 3, 4].

What happens instead

flatten_nested_categories([1, [2, [3, 4]]]) returns [1, 2, [3, 4]] with inner array still unflattened.

function flatten_nested_categories(categories) {
  return categories.flat();
}

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 logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

Flattening nested category list leaves inner arrays unflattened

What it should do

What happens instead

More logic errors to practise

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Flattening nested category list leaves inner arrays unflattened

What it should do

What happens instead

More logic errors to practise

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