locale semi-agnostic string to float conversion [JavaScript]

.gitignore

# Editor backup files
*.bak
*~

cvt.js

// parseFloat() but now locale aware and trying to be locale agnostic
//
// put in closure to cache intel which you don't want to calc each time
// you convert a string --> float
function StrToFloat() {
  var decimal_point = (1.1).toLocaleString().substr(1,1);
  var K_separator = (5000).toLocaleString().substr(1,1);
  if (K_separator === '0')
    K_separator = (decimal_point === '.' ? ',' : '.');

  return function(str) {
    switch (typeof(str)) {
    case 'float':
    case 'integer':
      return str;

    default:
      str = '' + str; // force str to be string type
      str = str.match(/[0-9.,eE-]+/);
      if (str)
        str = str[0];
      else
        return Number.NaN; // VERY illegal number format

      var kp = str.indexOf(',');
      var dp = str.indexOf('.');
      var kpl = str.lastIndexOf(',');
      var dpl = str.lastIndexOf('.');
      // can we be 'locale agnostic'? We can if both markers are in the input:
      if (kp > 0 && dp > 0) {
        if (kp < dp) {
          // e.g.: 1,000.00
          if (kpl > dpl || dpl > dp)
            return Number.NaN; // VERY illegal number format
          str = str.replace(/,/g, '');
        } else {
          // e.g.: 1.000,00
          if (kpl < dpl || kpl > kp)
            return Number.NaN; // VERY illegal number format
          str = str.replace(/\./g, '').replace(',', '.');
        }
      } else {
        // only one of 'em in there: must we use the detected 'current' locale
        // or can we 'heuristically determine' what's right here?
        // We can do the latter if we have either:
        // - only up to 2 digits following the only separator
        // - more than 3 digits following the only separator
        // - one separator only and the number starts with it, e.g. '.45'
        //
        // When we have only 3 digits following the last and only sep, we assume the separator
        // to be a 'thousands marker'.
        // We COULD fall back to the current locale, but than the ambiguous items receive
        // different treatment on a possibly incorrect locale setting (e.g. my machines are all
        // US/metric configured while I live in the Netherlands, but I /despise/ Dutch MS Excel,
        // for example. Riding the 'locale aware' ticket would definitely screw up my [ambiguous]
        // numbers. I believe it's better to be consistently wrong than semi-randomly correct.
        //
        // examples: 1.000 : 5,00 : 2,999.95 : 2,998 : 7.50 : 0,1791634 : 0.1791634 : .45 : ,32
        if (dp >= 0 && kp < 0) {
          // .45, ....
          if (dp !== 0 && (dpl > dp || str.substr(dp + 1).match(/^[0-9]{3}\b/)))
            str = str.replace(/\./g, '');
        } else if (kp >= 0 && dp < 0) {
          // ,32; ....
          if (kp !== 0 && (kpl > kp || str.substr(kp + 1).match(/^[0-9]{3}\b/)))
            str = str.replace(/,/g, '');
          else
            str = str.replace(',', '.');
        } else if (kp < 0 && dp < 0) {
          // integer value
        } else {
          // VERY illegal format, such as '.456,678'
          return Number.NaN;
        }
      }
      // now str has parseFloat() compliant format with US decimal point
      // only (iff it has a decimal fraction at all).
      return parseFloat(str);
    }
  };
}


$$('.chooseout a').addEvent('click', function(e) {
  e.stop();
  var cvt = StrToFloat();
  console.log('examples: 1.000 : ', cvt('1.000'));
  console.log('examples: 1.000.000 : ', cvt('1.000.000'));
  console.log('examples (India/US): 1.00.000 : ', cvt('1.00.000'));
  console.log('examples: 5,00 : ', cvt('5,00'));
  console.log('examples: 2,999.95 : ', cvt('2,999.95'));
  console.log('examples: 2,999.995 : ', cvt('2,999.995'));
  console.log('examples: 2.999,95 : ', cvt('2.999,95'));
  console.log('examples: 2.999,995 : ', cvt('2.999,995'));
  console.log('examples: 2,998 : ', cvt('2,998'));
  console.log('examples: 2,999,998 : ', cvt('2,999,998'));
  console.log('examples (India): 2,99,998 : ', cvt('2,99,998'));
  console.log('examples: 7.50 : ', cvt('7.50'));
  console.log('examples: 0,1791634 : ', cvt('0,1791634'));
  console.log('examples: 0.1791634 : ', cvt('0.1791634'));
  console.log('examples: .45 : ', cvt('.45'));
  console.log('examples: ,32 : ', cvt(',32'));
  console.log('examples: .450 : ', cvt('.450'));
  console.log('examples: ,320 : ', cvt(',320'));

  console.log('examples FLOAT: 3.1415 : ', cvt(3.1415));
  console.log('examples INT: 1234 : ', cvt(1234));

  console.log('examples: 1 EUR : ', cvt('1 EUR'));

  console.log('examples BAD: bla : ', cvt('bla'));
  console.log('examples BAD: .456,678 : ', cvt('.456,678'));
  console.log('examples BAD: ,456.678 : ', cvt(',456.678'));
  console.log('examples BAD: .123.456,678 : ', cvt('.123.456,678'));
  console.log('examples BAD: ,123,456.678 : ', cvt(',123,456.678'));
  console.log('examples BAD: .456,678.456 : ', cvt('.456,678.456'));
  console.log('examples BAD: ,456.678,456 : ', cvt(',456.678,456'));
  console.log('examples BAD: 1.456,678.456 : ', cvt('1.456,678.456'));
  console.log('examples BAD: 1,456.678,456 : ', cvt('1,456.678,456'));

  var preis_str = $('getContent').getElement('.article_price b').get('text');
  // BTW: NEVER do a toInt() as you'll lose the fractional part in the price.
  var preis = cvt(preis_str);
  var spreis_set = $$(".gespreis");
  var summe = spreis_set[0].get('text');
  summe = cvt(summe);
  summe += preis;
  console.log('summe: ', summe);

  spreis_set.each(function(el) {
    el.set('text', summe.toFixed(2));
  });
});

index.html

<!DOCTYPE html>
<html>
<head>
    <meta content="text/html; charset=utf-8">
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/mootools/1.4.5/mootools.js"></script>
</head>
<body>
    <div id="getContent">
        <div class="article_price">
            Preis: <b>99,66</b> &euro;
            <span>auch mit elektronischer Zeitschaltuhr</span>
        </div>
    </div>

    <div class="chooseout">
        <a class="btn-2011 rsblue" href="javascript:void(0);">
            <span class="btn-2011-glass"></span>In den Warenkorb
        </a>
    </div>

    <div id="warentext" >
        <p>Leider ist dieser Artikel unverk&auml;uflich denn sie existiert nur
        virtuell.</p>
        <p>Dennoch freuen wir uns sehr, dass Du bereit warst, die immense
        Summe von <span class="gespreis">0</span> Euro f&uuml;r diese
        Produkte zu bezahlen.
        Falls Du Dich jetzt fragst: Was soll ich mit den
        <span class="gespreis">0</span> Euro anfangen, von denen ich mich
        bereits verabschiedet habe, gibt es einen Vorschlag: SPENDEN</p>
    </div>

    <script type="text/javascript" src="cvt.js"></script>
</body>
</html>

This won't work for '1.233'
Is: 1233,
expected: 1.233