repeatArray

1/**
2 * Returns a new array with the input array repeated a specified number of times.
3 *
4 * @param arr - The array to repeat.
5 * @param times - The number of times to repeat the array. Must be a non-negative integer.
6 * @returns A new array with repeated content.
7 */
8export function repeatArray<T>(arr: T[], times: number): T[] {
9  if (!Number.isInteger(times) || times < 0) {
10    throw new Error('"times" must be a non-negative integer');
11  }
12  return Array.from({ length: times }, () => arr).flat();
13}

• Concise and expressive

  Utilizes Array.from with flat() for compact, readable logic that avoids verbose loop code.

• Immutability

  Returns a new array without modifying the original, adhering to functional programming principles.

• Robust parameter validation

  Throws an explicit error if times is not a non-negative integer, helping avoid silent runtime bugs.

• Generic type-safe implementation

  Fully generic using T[], preserving type correctness across repeated segments.

• Efficient for small to medium repetitions

  Performance is suitable for UI and general logic use cases where repetitions are not excessive.

Tests | Examples

1test('repeatArray - repeat 3 times', () => {
2  expect(repeatArray([1, 2], 3)).toEqual([1, 2, 1, 2, 1, 2]);
3});
4
5test('repeatArray - repeat 1 time', () => {
6  expect(repeatArray(['a'], 1)).toEqual(['a']);
7});
8
9test('repeatArray - repeat 0 times', () => {
10  expect(repeatArray([42], 0)).toEqual([]);
11});
12
13test('repeatArray - empty array', () => {
14  expect(repeatArray([], 5)).toEqual([]);
15});
16
17test('repeatArray - throws on negative times', () => {
18  expect(() => repeatArray([1, 2], -1)).toThrow();
19});
20
21test('repeatArray - throws on non-integer times', () => {
22  expect(() => repeatArray([1, 2], 2.5)).toThrow();
23});

Common Use Cases

• Mock data generation

  Repeating sample structures to fill space or test pagination, infinite scroll, or list rendering behavior.

• CSS grid and layout scenarios

  Useful for replicating component instances when templating UI elements in predictable patterns.

• Test data or load simulation

  Creating longer sequences of predefined values for testing performance or user interaction behavior.

• Repeating audio/video frames or instructions

  Helpful in media and game development where sequences need to loop a fixed number of times.

• Form input presets

  Prefilling form fields with repeated options or default sets based on user-defined length.