function $(id)
{
	if(document.getElementById(id))
		return document.getElementById(id);
	else {
		alert("Elemento " + id + " não definido.");
		return null;
	}
}



function $_C(id)
{
	if(document.getElementById(id))
		return true;
	else 
		return false;
}



function createElement(id)
{
	return document.createElement(id);	
}


function removeElement(father_id, child_id) 
{
	var d = $(father_id); 
	
	if($(String(child_id)))
	{
		var d_nested = $(String(child_id)); 
		var throwawayNode = d.removeChild(d_nested);
	}
}



function createCamada(page_id, id)
{
	if(!$(String(id)))
	{
		var div = $(String(page_id)); 
		var ele = createElement("div");
		ele.id = id;
	
		div.appendChild(ele);
	}

	else {
		removeElement(page_id, id); 
	}
}


function hiddenElement(id) 
{
	$(id).style.visibility =  "hidden";
}



function addTextNode(target_id, text)
{
	alert(target_id);
	var newtext = document.createTextNode(text);
	var para    = $(target_id);
	
	para.appendChild(newtext);
}


function displayElement(id) 
{
	if($(String(id)).style.visibility ==  "hidden") {
		$(String(id)).style.visibility =  "visible";
		return true;
	}	
	else {
		hiddenElement(String(id));  
		return false;
	}
}


function deleteElement(id) 
{
	var d = $("principal"); 
	
	if($(String(id)))
	{
		var d_nested = $(String(id)); 
		var throwawayNode = d.removeChild(d_nested);
	}
}


/*
<iframe id="iframe_js" name="iframe_js" 
style="width:0px; height:0px; border: 0px"
src="blank.html">
</iframe>
*/
function createIframeHidden()
{
	var iframe 			 = createElement("iframe");
	iframe.id     		 = "iframe_js";
	iframe.name   		 = "iframe_js";
	iframe.style.display = "0px";
	iframe.src    		 = "blank.html";

	document.getElementsByTagName("body")[0].appendChild(iframe);
}



function targetLinks(id, target)
{
	var div   = $(id);
	var links = div.getElementsByTagName("a");

	for (var i = 0; i < links.length; i++) { 
		links[i].target = target;
	}
}



function targetForm(id, target)
{
	var div   = $(id);
	var forms = div.getElementsByTagName("form");

	for (var i = 0; i < forms.length; i++) { 
		forms[i].target = target;
	}
}



function formId2Name(form_id)
{
	var form = $(form_id);
	var tam  = form.length;

	for (var i = 0; i < tam; i++) { 
		form[i].name = form[i].id;
	}
}