Javascript code to convert numbers to words in British system

number_to_words.js

function inWords(numIn) {
  var inWordsSub = function(num) {
    var a = ['', 'One ', 'Two ', 'Three ', 'Four ', 'Five ', 'Six ', 'Seven ', 'Eight ', 'Nine ', 'Ten ', 'Eleven ', 'Twelve ', 'Thirteen ', 'Fourteen ', 'Fifteen ', 'Sixteen ', 'Seventeen ', 'Eighteen ', 'Nineteen '];
    var b = ['', '', 'Twenty', 'Thirty', 'Forty', 'Fifty', 'Sixty', 'Seventy', 'Eighty', 'Ninety'];
    var n = ('0000000' + num).substr(-7).match(/^(\d{2})(\d{2})(\d{1})(\d{2})$/);
    if (!n) return;
    var str = '';
    str += (n[1] != 0) ? (a[Number(n[1])] || b[n[1][0]] + ' ' + a[n[1][1]]) + 'Lakh ' : '';
    str += (n[2] != 0) ? (a[Number(n[2])] || b[n[2][0]] + ' ' + a[n[2][1]]) + 'Thousand ' : '';
    str += (n[3] != 0) ? (a[Number(n[3])] || b[n[3][0]] + ' ' + a[n[3][1]]) + 'Hundred ' : '';
    str += (n[4] != 0) ? ((str != '') ? 'and ' : '') + (a[Number(n[4])] || b[n[4][0]] + ' ' + a[n[4][1]]) : '';
    return str;
  }
  var nTemp = numIn.toString().split(".");
  var num = nTemp[0].split(",").join("");
  if (num.length > 14) return 'overflow';
  num = ('00000000000000' + num).substr(-14);
  var words = inWordsSub(num.substr(-7))
  var croreWords = inWordsSub(num.substr(0, 7))
  if (croreWords != "") {
    words = croreWords + " Crore " + words;
  }
  return words;
}