How to Create a Pyramid Array in Javascript

The challenge

Write a function that when given a number >= 0, returns an Array of ascending length subarrays.

pyramid(0) => [ ]
pyramid(1) => [ [1] ]
pyramid(2) => [ [1], [1, 1] ]
pyramid(3) => [ [1], [1, 1], [1, 1, 1] ]

Note: the subarrays should be filled with 1s

The solution in Javascript

Option 1:

function pyramid(n) {
  const res = [];
  for(let i = 0; i < n; i++){
    res.push([...Array(i+1)].fill(1))
  }
  return res;
}

Option 2:

function pyramid(n) {
  return Array(n).fill().map((e,i)=>Array(i+1).fill(1))
}

Option 3:

const pyramid = n => Array(n).fill(1).map((x, i) => Array(i + 1).fill(1))

Test cases to validate our solution

describe('basic tests', () => {
  it("Testing for 0", () => assert.deepEqual(pyramid(0), []));
  it("Testing for 1", () => assert.deepEqual(pyramid(1), [[1]]));
  it("Testing for 2", () => assert.deepEqual(pyramid(2), [[1], [1, 1]]));
  it("Testing for 3", () => assert.deepEqual(pyramid(3), [[1], [1, 1], [1, 1, 1]]));
});