isSequentialNumber.js

function isSequentialNumber(code, reversed) {
  var codeArr = code.split(''),
    i,
    total = codeArr.length;
  if (reversed) {
    codeArr = codeArr.reverse();
  }
  for (i = 0; i < total - 1; i = i + 1) {
    if (Number(codeArr[i + 1]) !== Number(codeArr[i]) + 1) {
      return false;
    }
  }
  return true;
}