Resolving IDNA urls in browser javascript

A handy feature I discovered a while ago: resolving (for want of a better word -- I can't make up my mind whether to call turning Unicode to ASCII encoding or decoding in this context :-) IDNA URLs (RFC 3490: International Domain Names in Applications) is a breeze:

function resolveIDNA(url) {
  var a = document.createElement("a");
  a.href = url;
  return a.href;
}

Test your browser, or try your own IDN domains!

It doesn't seem to work in all browsers yet, though; of those I've tested, Firefox 3 and Safari 3 both support it, whereas Opera 10.4.11 and Google Chrome 1.0.154.65 do not.

Update: Both as my google memory didn't find this when I sought it out (decoding a non-ASCII, non-IDNA-encoded hostname to its punycode/IDNA-encoded ASCII counterpart), and for having found a use for this in the wild, here is the altered function that just takes a unicode hostname and turns it into its punycode/IDNA form:

function IDNAtoASCII(hostname) {
  var a = document.createElement("a");
  a.href = "http://" + hostname + "/";
  return a.hostname;
}