How do I check whether a jQuery element is in the DOM?

Let's say that I define an element开发者_运维问答

$foo = $('#foo');

and then I call

$foo.remove()

from some event. My question is, how do I check whether $foo has been removed from the DOM or not? I've found that $foo.is(':hidden') works, but that would of course also return true if I merely called $foo.hide().

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Like this:

if (!jQuery.contains(document, $foo[0])) {
    //Element is detached
}

This will still work if one of the element's parents was removed (in which case the element itself will still have a parent).

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How about doing this:

$element.parents('html').length > 0

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I just realized an answer as I was typing my question: Call

$foo.parent()

If $f00 has been removed from the DOM, then $foo.parent().length === 0. Otherwise, its length will be at least 1.

[Edit: This is not entirely correct, because a removed element can still have a parent; for instance, if you remove a <ul>, each of its child <li>s will still have a parent. Use SLaks' answer instead.

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Since I'm unable to respond as a comment (too low karma I guess), here's a full reply. The fastest way is easily to unroll the jQuery check for browser support and to shave the constant factors to minimum.

As seen also here - http://jsperf.com/jquery-element-in-dom/28 - the code would look like this:

var isElementInDOM = (function($) {
  var docElt = document.documentElement, find,
      contains = docElt.contains ?
        function(elt) { return docElt.contains(elt); } :

        docElt.compareDocumentPosition ?
          function(elt) {
            return docElt.compareDocumentPosition(elt) & 16;
          } :
          ((find = function(elt) {
              return elt && (elt == docElt || find(elt.parentNode));
           }), function(elt) { return find(elt); });

  return function(elt) {
    return !!(elt && ((elt = elt.parent) == docElt || contains(elt)));
  };
})(jQuery);

This is semantically equivalent to jQuery.contains(document.documentElement, elt[0]).

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Probably the most performative way is:

document.contains(node); // boolean

This also works with jQuery:

document.contains($element[0]); // var $element = $("#some-element")
document.contains(this[0]); // in contexts like $.each(), `this` is the jQ object

Source from MDN

Note:

• Internet Explorer only supports contains() for elements.

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instead of iterating parents you can just get the bounding rect which is all zeros when the element is detached from dom

function isInDOM(element) {
    var rect=element.getBoundingClientRect();
    return (rect.top || rect.bottom || rect.height || rect.width)?true:false;
}

if you want to handle the edge case of a zero width and height element at zero top and zero left you can double check by iterating parents till the document.body

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I liked this approach. No jQuery and no DOM search. First find the top parent (ancestor). Then see if that is the documentElement.

function ancestor(HTMLobj){
  while(HTMLobj.parentElement){HTMLobj=HTMLobj.parentElement}
  return HTMLobj;
}
function inTheDOM(obj){
  return ancestor(obj)===document.documentElement;
}

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Agree with Perro's comment. It can also be done like this:

$foo.parents().last().is(document.documentElement);

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jQuery.fn.isInDOM = function () {
   if (this.length == 1) {
      var element = this.get(0);
      var rect = element.getBoundingClientRect();
      if (rect.top + rect.bottom + rect.width + rect.height + rect.left + rect.right == 0)
         return false;
      return true;
   }
   return false;
};

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Why not just: if( $('#foo').length === 0)... ?

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if($foo.nodeType ){ element is node type}