TypeScript recursive power function

2014-12-26 (Friday) | 100 words (~1 minutes reading)

This is a productOfArray(numbers) function in TypeScript that uses recursion.

function productOfArray(numbers: number[]): number {
  if (numbers.length === 0) {
    return 0;
  }
  if (numbers.length === 1) {
    return numbers[0];
  }
  return numbers[0] * productOfArray(numbers.slice(1));
}

Jest tests:

describe(productOfArray.name, () => {
  test("multiplies array elements together", () => {
    expect(productOfArray([])).toBe(0);
    expect(productOfArray([5])).toBe(5);
    expect(productOfArray([1, 2, 3])).toBe(6);
    expect(productOfArray([5, 5, 5])).toBe(125);
    expect(productOfArray([8, 8])).toBe(64);
    expect(productOfArray([1, 2, 3, 4, 5, 6, 7, 8, 9])).toBe(362880);
  });
});

Tech mentioned