function changeNumberFormatTo(lang) {
  var val = this + "";
  var lang = lang.toLowerCase();
  
  if( lang.search(/ger/) > -1 || lang.search(/deu/) > -1 ) {
    return val.replace(/,/g, "").replace(/[.]/g, ",");
  } else if( lang.search(/eng/) > -1 ) {
    return val.replace(/[.]/g, "").replace(/,/g, ".");
  } else {
    return val;
  }
}

String.prototype.changeNumberFormatTo = changeNumberFormatTo;
Number.prototype.changeNumberFormatTo = changeNumberFormatTo;