// funções para manipular classes de objetos DOM //
function getArrayFromClasses( obj )
{
  var classes = obj.className.split(" ");
  if( classes.length == 1 && classes[0] == "" )
  {
    classes = new Array();
  }  
  
  return classes;
}

function setClassesStringFromArray( classes )
{
  return classes.join(" ");
}

function addClass( obj, className )
{
  var classes = getArrayFromClasses( obj );
  classes.push( className );
  obj.className = setClassesStringFromArray( classes );
}

function removeClass( obj, className )
{
  var classes = getArrayFromClasses( obj );
  for(i in classes)
  {
    if(classes[i] == className)
    {
      classes.splice(i,1);
    }
  }
  obj.className = setClassesStringFromArray( classes );  
}

function clearClasses( obj )
{
  var classes = new Array();
  obj.className = setClassesStringFromArray( classes );
}

function existsClass( obj, className )
{
  var classes = getArrayFromClasses( obj );
  for(i in classes)
  {
    if(classes[i] == className)
    {
      return true;
    }
  }
  return false;
}