sample

1/**
2 * Returns a new array with a specified number of unique random elements.
3 *
4 * @param arr - The input array to sample from.
5 * @param count - The number of random elements to select.
6 * @returns A new array with randomly selected elements (no duplicates).
7 */
8export function sample<T>(arr: T[], count: number): T[] {
9  const result: T[] = [];
10  const copy = [...arr];
11
12  while (result.length < count && copy.length) {
13    const index = Math.floor(Math.random() * copy.length);
14    result.push(copy.splice(index, 1)[0]);
15  }
16
17  return result;
18}

1test('sample returns correct count', () => {
2  const result = sample([1, 2, 3, 4, 5], 3);
3  expect(result.length).toBe(3);
4});
5
6test('sample returns unique values', () => {
7  const input = [1, 2, 3, 4, 5];
8  const result = sample(input, 5);
9  const unique = new Set(result);
10  expect(unique.size).toBe(result.length);
11});
12
13test('sample never returns elements outside input', () => {
14  const input = ['a', 'b', 'c'];
15  const result = sample(input, 2);
16  result.forEach((val) => expect(input).toContain(val));
17});
18
19test('sample handles count larger than input gracefully', () => {
20  const input = [1, 2];
21  const result = sample(input, 5);
22  expect(result.length).toBe(2);
23  expect(result).toEqual(expect.arrayContaining(input));
24});