function nl2br (str, replaceMode, isXhtml) {
  var breakTag = (isXhtml) ? '<br />' : '<br>';
  var replaceStr = (replaceMode) ? '$1'+ breakTag : '$1'+ breakTag +'$2';
  return (str + '').replace(/([^>\r\n]?)(\r\n|\n\r|\r|\n)/g, replaceStr);
}

function br2nl (str, replaceMode) {   
  var replaceStr = (replaceMode) ? "\n" : '';
  // Includes <br>, <BR>, <br />, </br>
  return str.replace(/<\s*\/?br\s*[\/]?>/gi, replaceStr);
}