/*
  Copyright Robert Nyman, http://www.robertnyman.com
  Free to use if this text is included
*/
// ---
function $(strId, nullOk){
  var result = document.getElementById(strId);
  if (result || nullOk) {
      return result;
  } else {
      throw 'DOM element "' + strId + '" does not exist.';
  }
}
// ---
function getElementsByClassName(oElm, strTagName, strClassName){
  var arrElements = (strTagName == "*" && oElm.all)? oElm.all : oElm.getElementsByTagName(strTagName);
  var arrReturnElements = new Array();
  strClassName = strClassName.replace(/\-/g, "\\-");
  var oRegExp = new RegExp("(^|\\s)" + strClassName + "(\\s|$)");
  var oElement;
  for(var i=0; i<arrElements.length; i++){
    oElement = arrElements[i];    
    if(oRegExp.test(oElement.className)){
      arrReturnElements.push(oElement);
    } 
  }
  return (arrReturnElements)
}
// ---
function hasClassName(oElement, strClassName){
  strClassName = strClassName.replace(/\-/g, "\\-");
  var oRegExp = new RegExp("(^|\\s)" + strClassName + "(\\s|$)");
  return oRegExp.test(oElement.className);
}
// ---
function addClassName(oElm, strClassName){
  var strCurrentClass = oElm.className;
  if(!new RegExp(strClassName, "i").test(strCurrentClass)){
    oElm.className = strCurrentClass + ((strCurrentClass.length > 0)? " " : "") + strClassName;
  }
}
// ---
function removeClassName(oElm, strClassName){
  var oClassToRemove = new RegExp((strClassName + "\s?"), "i");
  oElm.className = oElm.className.replace(oClassToRemove, "").replace(/^\s?|\s?$/g, "");
}
// ---