Locale-based short date formatting

gistfile1.js

var getShortDateFormat = (function() {
  var pattern = undefined,
      defaultPattern = "M/d/yyyy",
      localeFormatMappings = {
        "en-us": "M/d/yyyy",
        "ja-jp": "yyyy\u5E74 M\u6708 d\u65E5"
      };

  return function(date, locale) {
    var m, d, y;

    locale = locale || "";
    locale = locale.toLowerCase();
    pattern = localeFormatMappings[locale] || defaultPattern;

    return pattern.replace('yyyy', y = '' + date.getFullYear())
      .replace('yy', y.substring(2))
      .replace('MM', zeroPad(m = date.getMonth() + 1))
      .replace('M', m)
      .replace('dd', zeroPad(d = date.getDate()))
      .replace('d', d);
  }

  function zeroPad(n) {
    return (+n < 10 ? '0' : '') + n;
  }
})();

alert(getShortDateFormat(new Date(), "en-US"));
alert(getShortDateFormat(new Date(), "ja-jp"));
alert(getShortDateFormat(new Date()));

Most of the function came from this SO answer: http://stackoverflow.com/a/3187610/18265.