euler 3 first goes

// First attempt - errors on x<2
// with 1 param
var largestprimefactor = function (x) {
  return (function recur(v, d) {
    if (v === d) return v;
    if (v % d == 0) return recur(v / d, d);
    return recur(v, d + 1);
  }(x, 2));
};
// with two params
var largestprimefactor = function recur(x, d) {
  if (v === d) return v;
  if (v % d == 0) return recur(v / d, d);
  return recur(v, d + 1);
};