check if cached jquery object is still in DOM

Question

Hi all:

Does anyone know how to tell if a cached jQuery object has gone stale, e.g. is no longer in the DOM? For example:

var $cached_elem = $('.the_button');

// .. and then later

$cached_elem.text('updating...');

I have recently encountered the situation where the $cached_elem is removed from the DOM due to some other event. So what I would like to do:

if ( $cache_elem.isStillInDOM() ){
  // now do time consuming stuff with $cached_elem in DOM 
}

Before anyone offers, I have already employed this, which is a fair analog for what I'm trying to do:

if ( $cached_elem.is(':visible') === true ){ ... }

However, this is not really the same thing and could fail in some cases.

So can anyone think of a simple way to check directly if a cached jQuery object is "stale"? I may be forced to write a plugin if not ...

Answer 1

If the selector hasn't changed, just reinitialize it:

var $cached_elem = $('.the_button');
// code that might remove some elements of $cached_elem
$cached_elem = $('.the_button');

If you want to avoid duplicating the selector string, use the selector property of the original jQuery object:

var $cached_elem = $('.the_button');
// code that might remove some elements of $cached_elem
$cached_elem = $($cached_elem.selector);
if ($cached_elem.length) {
  // element still exists
}

Answer 2

if($elem.closest('body').length > 0) seems like it could do the trick.

jsFiddle example

Edit: Updated in response to Yi Jiang's comment so that it will return correctly if its parent element is removed

Edit 2: Updated in response to lonesomeday's comment - changed parents() to 'closest()` for performance improvement