Pascal's triangle with n level

pascals-triangle-with-n-level.js

// Time complexity: O(n ^ 2) where is the number of levels and
//                  another n is for the number of elements in each level.
// Space complexity: O(2n + 1) to hold all elements, which is linear space.
function pascalTriangle(level) {
    if (level === 0) return [];
    if (level === 1) return [1];
    if (level === 2) return [1, 1];

    const d = Array.from(Array(level), () => []);

    d[0] = [1];
    d[1] = [1, 1];

    for (let i = 2; i < level; i += 1) {
        const arr = Array.from(Array(i + 1), () => 1);

        for (let j = 1; j < i; j += 1) {
            arr[j] = d[i - 1][j - 1] + d[i - 1][j];
        }

        d[i] = arr;
    }

    return d;
}

function main() {
    Array.from(Array(20), (_, i) => {
       console.log(`Pascal's triangle with %d level(s): `, i, pascalTriangle(i)); 
    });
}

console.clear();
main();