const numRows = 5⏎
⏎
var generate = function (numRows) {⏎
  const triangle = [[1], [1, 1]]⏎
⏎
  if (numRows === 0) {⏎
    return []⏎
  } else if (numRows === 1) {⏎
    return [[1]]⏎
  } else if (numRows === 2) {⏎
    return [[1], [1, 1]]⏎
  } else {⏎
    for (let i = 2; i < numRows; i++) {⏎
      addRow(triangle)⏎
    }⏎
  }⏎
  return triangle⏎
}⏎
var addRow = function (triangle) {⏎
  const previous = triangle[triangle.length - 1]⏎
  const newRow = [1]⏎
  for (let i = 0; i < previous.length - 1; i++) {⏎
    const current = previous[i]⏎
    const next = previous[i + 1]⏎
    newRow.push(current + next)⏎
  }⏎
  newRow.push(1)⏎
  return triangle.push(newRow)⏎
}⏎
⏎
generate(numRows)⏎