Functions with unknown amount of args.

Is this (see listing) possible with espruino javascript.

function add() {
  var i, len, result = 0;
  for (i = 0; len = arguments.length; i < len; ++i) {
  result += arguments[i];
  }
  return result;
}

add(3, 7, 4, 6);  //result = 20