Detect if a jQuery object is on the page or not

Question

Given a jQuery object, $j, I need to know if it represents something that is already on the page or if it is something that has not yet been put on the page. Fo

Answer 1

I'd probably just check to see if the element can reach the body element:

$j.closest('body').size()>0

As you noted in other comments, this would fail in some exceptional cases where you are handling extra body elements. If you really want to detect those situations, I guess you could check to see if you have multiple $(body) elements but I suspect that such extreme cases will get out of control pretty quickly.

This "is-probably-attached-to-page" check could be turned in to a bona-fide jQuery selector, too:

$.expr[':'].isProbablyAttached = function(obj){

    return $(obj).closest('body').size()>0;
};

// Usage:
$('.someClasses:isProbablyAttached').doSomething();