index.js

for (let i = 0; i < 10; i++) {
  for (let j = 0; j < 10; j++) {
    const isFilled =
      i === 0 ||
      i === 9 ||
      j === 0 ||
      j === 9 ||
      i === j ||
      i === 9 - j
    process.stdout.write(isFilled ? '#' : ' ')
    if (j === 9) {
      console.log()
    }
  }
}