function trim(str)
  {
    return str.replace(/^\s*|\s*$/g,"");
  }

  function formatTel(str)
  {
    str = str.replace(/ -/g,'-');
    str = str.replace(/- /g,'-');
    str = str.replace(/-/g,' - ');
    return str;
  }

  function keepOnly(charsToKeep,str){
    var i,curChar;
    var retStr = '';
    str = trim(str);
    var laenge = str.length;
    for(i=0; i<laenge; i++){
      curChar = str.charAt(i);
      if(charsToKeep.indexOf(curChar)>=0)
        retStr += curChar;
    }
    return retStr;
  }