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Test cases
Language
JavaScript
TypeScript
export default function flattenOnce(arr) { // TODO: Flatten one level deep throw new Error('Not implemented'); }
import flattenOnce from './flattenOnce'; describe('flattenOnce', () => { test('flattens a simple nested array', () => { expect(flattenOnce([1, [2, 3], [4, [5]]])).toEqual([1, 2, 3, 4, [5]]); }); test('returns same array when already flat', () => { expect(flattenOnce([1, 2, 3])).toEqual([1, 2, 3]); }); test('handles mixed array contents', () => { expect(flattenOnce([[1], 2, [3, [4]], 5])).toEqual([1, 2, 3, [4], 5]); }); test('returns empty array for empty input', () => { expect(flattenOnce([])).toEqual([]); }); });
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