/*----------------------------------------------------------------------------------------------
DESCRIPTION: returns true if the image is valid
------------------------------------------------------------------------------------------------*/
function isImage(str)
{
  extension = (str.substring(str.lastIndexOf("."))).toLowerCase(); 	
  extensiones_permitidas = new Array(".jpg",".JPG",".png",".PNG",".jpeg",".JPEG",".gif",".GIF"); 
  permitida = false; 
  
  for (var i = 0; i < extensiones_permitidas.length; i++)
  { 
    if(extensiones_permitidas[i] == extension)
	{ 
	  permitida = true; 
	  break; 
    } 
  } 
  
  return permitida;
}
/*----------------------------------------------------------------------------------------------
DESCRIPTION: returns true if the string is not empty.
------------------------------------------------------------------------------------------------*/
function isRequired(str){
	return (str == null) || (str.length == 0);
}
/*----------------------------------------------------------------------------------------------
DESCRIPTION: returns true if the string is a valid email.
------------------------------------------------------------------------------------------------*/
function isEmail(str){
	if(isRequired(str)) return false;
	var re = /^[^\s()<>@,;:\/]+@\w[\w\.-]+\.[a-z]{2,}$/i
	return re.test(str);
}