Check if element exists

Question

Possible Duplicates:
Is there an “exists” function for jQuery
jQuery determining if element exists on page

if(tr) is returning true when tr is not an element, how do I check whether it's an element that exists?

var tr = $('#parts-table .no-data').parent();
$('.delete', row).bind('click', function (e) {
  that.delete(e.currentTarget);
});
console.log(tr);
if (tr) //returns true when it shouldn't

The reason why it evaluates to true is because you get a jQuery object whether it finds elements or not, which is always considered true. — BoltClock, Jan 25 '11 at 16:16
Would it have been so hard to unindent your code before posting it? — user229044, Jan 25 '11 at 16:17
Possible duplicate: http://stackoverflow.com/questions/4257906/jquery-determining-if-element-exists-on-page — Richard Marskell - Drackir, Jan 25 '11 at 16:18
duplicate: http://stackoverflow.com/questions/477667/how-to-check-null-objects-in-jquery — naveen, Jan 25 '11 at 16:18
I went with 4257906 because it seemed like the closest match. — T.J. Crowder, Jan 25 '11 at 16:20
This is somewhat a dupe (I voted to close), but at the same time, I think the question is more 'Why does a jQuery object always evaluate to true?' So perhaps it shouldn't be closed? Opinions? — karim79, Jan 25 '11 at 16:22
@webnet: pal its asked many times... why dont you check before hand... — naveen, Jan 25 '11 at 16:23
@karim79: http://docs.jquery.com/Frequently_Asked_Questions#How_do_I_test_whether_an_element_exists.3F — naveen, Jan 25 '11 at 16:23

karim79 · Accepted Answer · 2011-02-17T00:42:02.290

36

Check its length property:

if(tr.length) {
    // exists
}

if(tr) always evaluates to true because a jQuery object, or any JavaScript Object for that matter, is always truthy.

edited Feb 17 '11 at 00:42

answered Jan 25 '11 at 16:15

karim79

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score 8 · Answer 2 · answered Jan 25 '11 at 16:26

I always add this little jQuery snippet at the beginning of my JS files

jQuery.fn.exists = function(){return jQuery(this).length>0;}

This uses the same approach many here have suggested, but it also allows you to access whether or not an object exists like this:

if ( $('#toolbar').exists() ){
    $('#toolbar').load(..., function(){...});
    //etc...
}

T.J. Crowder · Answer 3 · 2011-07-31T22:02:05.907

3

That's because tr is a jQuery object, which is truthy (even when the jQuery object is empty). Use if (tr.length) instead, which will be true when length is not zero, false when it is zero. Or alternately, if (tr[0]).

edited Jul 31 '11 at 22:02

answered Jan 25 '11 at 16:15

T.J. Crowder

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score 1 · Answer 4 · answered Jan 25 '11 at 16:17

1

How about:

if (tr.size() == 0)

answered Jan 25 '11 at 16:17

Mark Robinson

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score 1 · Answer 5 · answered Jan 25 '11 at 16:23

1

try this

var tr = $('#parts-table .no-data').parent().length;

answered Jan 25 '11 at 16:23

Harish

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Check if element exists

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