hToD = function hToD(...h) {
  var hh = '00';
  if (h.length === 1) {
    hh = '' + h[0] + h[0];
  } else if (h.length === 2) {
    hh = '' + h[0] + h[1];
  }
  var d = parseInt(hh, 16);
  return !isNaN(d) ? d : 0;
}
Returns a base10 number from one or two hex digits
@param h
@returns {number}