document.getElementsByClassName = function(cl) 
{
	var retnode = [];
	var myclass = new RegExp('\\b'+cl+'\\b');
	var elem = this.getElementsByTagName('*');
	for (var i = 0; i < elem.length; i++)
	{
		var classes = elem[i].className;
		if (myclass.test(classes))
			retnode.push(elem[i]);
	}
	
	return retnode;
}; 


function changeImg(name, num)
{
    var tags = document.getElementsByClassName("images")[0].getElementsByTagName("a");
	    
    for (var i = 0; i < tags.length; i++)
	{
	    tags[i].className='';
	}

	tags[num].className='active';

	document.getElementById('mainImg').src = '/public/images/product/medium/'+name;
    document.getElementById('mainLink').href= '/public/images/product/large/'+name;
}