mini-nat.js

/* "a123b45c" → ["a", 123, "b", 45, "c"] */
function nat(x) {
  // digit-parts
  var d = x.split(/[^0-9]+/); // ["", "123", "45, ""]
  // alpha-parts
  var a = x.split(/[0-9]+/); // ["a", "b", "c"]
  // helpers
  function nonEmpty(x) { return x != "" }
  function toInt(x) { return x - 0 }
  // the one that does not start with a "" goes first
  var f = d[0]=="" ? a.filter(nonEmpty) : d.filter(nonEmpty).map(toInt);
  // the other one goes second
  var s = d[0]=="" ? d.filter(nonEmpty).map(toInt) : a.filter(nonEmpty);
  // intersperse/merge
  var r = [];
  for (var i=0; i<Math.max(f.length, s.length); i++) {
    if (i < f.length) r.push(f[i]);
    if (i < s.length) r.push(s[i]);
  }
  return r;
}