Return pascal`s triangle to desired depth

pascals_triangle.js

function pascalsTriange(depth) {
  let last = [1];
  let res = [];
  for (let i = 0; i < depth; i++) {
    let n = [];
    for (let j = 0; j < i + 1; j++) {
      n[j] = (last[j-1] || 0) + (last[j] || 0);
    }
    res.push(n);
    last = n;
  }
  return res;
}