Drowing a rhombus using the symbol '*' in a single line

rhombus.js

function rhombus(n) {
  return n < 0 || n % 2 == 0 ? null :
      [
        (n - (n % 2)) / 2,
        max => Array(max+1).fill(1).map((i, j) => ' '.repeat(max-j) + '*'.repeat(j*2+1)),
        half => half.concat(half.slice(0, -1).reverse(), '').join('\n')
      ]
      .reduce((curr, fn) => fn(curr));
  }
}