Mine

function getElementsByClassName(className, node)
{
	var children = null, returnArr = [], i;
	
	if (node == undefined) node = document.body;
	else if (typeof node != "object") return([]);
	else if (node.className == className)
		returnArr[returnArr.length] = node;
	
	children = (node.children) ? node.children : node.childNodes;
	for (i = 0; i < children.length; i++)
	{
		returnArr = returnArr.concat(
				getElementsByClassName( className, children[i] )
		);
	}
	
	return(returnArr);
}