Lakhs/Crores システムで数値を単語に効率的に変換するにはどうすればよいですか?

<code class="javascript">const a = ['', 'one ', 'two ', 'three ', 'four ', 'five ', 'six ', 'seven ', 'eight ', 'nine ', 'ten ', 'eleven ', 'twelve ', 'thirteen ', 'fourteen ', 'fifteen ', 'sixteen ', 'seventeen ', 'eighteen ', 'nineteen '];
const b = ['', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'];

function inWords (num) {
  if ((num = num.toString()).length > 9) return 'overflow';
  n = ('000000000' + num).substr(-9).match(/^(\d{2})(\d{2})(\d{2})(\d{1})(\d{2})$/);
  if (!n) return;
  let str = '';
  str += (n[1] != 0) ? (a[Number(n[1])] || b[n[1][0]] + ' ' + a[n[1][1]]) + 'crore ' : '';
  str += (n[2] != 0) ? (a[Number(n[2])] || b[n[2][0]] + ' ' + a[n[2][1]]) + 'lakh ' : '';
  str += (n[3] != 0) ? (a[Number(n[3])] || b[n[3][0]] + ' ' + a[n[3][1]]) + 'thousand ' : '';
  str += (n[4] != 0) ? (a[Number(n[4])] || b[n[4][0]] + ' ' + a[n[4][1]]) + 'hundred ' : '';
  str += (n[5] != 0) ? ((str != '') ? 'and ' : '') + (a[Number(n[5])] || b[n[5][0]] + ' ' + a[n[5][1]]) + 'only ' : '';
  return str;
}
````

This code combines pre-defined arrays 'a' and 'b' to form various numerical representations. By utilizing a regular expression, it captures the different sections of the number (e.g., crores, lakhs, thousands, hundreds, and ones) and generates the appropriate words. Importantly, this approach is much more concise than the earlier solution presented.

To demonstrate the code's functionality, an HTML/JavaScript snippet can be used:
</code>

document.getElementById('words').innerHTML = inWords(document.getElementById('number').value);