jQuery Find element else do nothing?

Question

I am trying to use jQuery to basically wrap a bunch of CSS modifications via jQuery but on pages where the IDs or Classes dont exist I get errors ? Like

jQuery(".class").css(random_stuff) is not a function

Any ideas what I can do to either find the elements and do nothing or ?

See this question http://stackoverflow.com/questions/31044/is-there-an-exists-function-for-jquery — Catfish, Mar 26 '10 at 19:21

score 5 · Accepted Answer · answered Mar 26 '10 at 19:13

5

In this case it looks like the jQuery library isn't being included correctly.

If jQuery finds nothing matching your selector, nothing will happen because it didn't find any elements to perform the action on, this is the default behavior.

answered Mar 26 '10 at 19:13

Nick Craver

623,446
136
1,297
1,155

That's a good point, jQuery doesn't throw if the return value is empty, it just doesn't do anything. – technophile Mar 26 '10 at 19:13
hey thanks - but if I want to try and "find and if cant find do nothing" how do I do this ? – Andrew Mar 26 '10 at 19:17
@Andrew the default chaining does this: `jQuery(".class").css(random_stuff)` nothing else...your error is the jQuery library not being included in the page properly. Try `alert(window.jQuery);` – Nick Craver Mar 26 '10 at 19:19
Andrew, you missed what Nick & technophile said. The "foo is not a function" error is thrown because jQuery is not included correctly. If a jQuery selector finds no matched elements, it returns an empty jQuery object and no errors are thrown on chained function calls. – Matt Ball Mar 26 '10 at 19:21

score 1 · Answer 2 · answered Mar 26 '10 at 19:16

1

Sounds like you are missing a reference to jQuery on those pages. jQuery only performs an action on the matched selection...it will not throw an error if nothing matches.

answered Mar 26 '10 at 19:16

Bradley Mountford

8,195
4
41
41

score 0 · Answer 3 · answered Mar 26 '10 at 19:11

0

if(jQuery(".class").length)
{
  jQuery(".class").css(random_stuff);
}

per Jquery Faq

You can use the length property of the jQuery collection returned by your selector:

answered Mar 26 '10 at 19:11

Matthew Vines

27,253
7
76
97

1

While this is accurate, it's an entirely superfluous check :) – Nick Craver Mar 26 '10 at 19:17
And while it's right 0 is falsy, I think it is still worth putting the extra `> 0` for readability :) – Chetan S Mar 26 '10 at 19:23

score 0 · Answer 4 · answered Mar 26 '10 at 19:13

0

You can check the return value's length property:

var myElement = $('.class');
if (myElement.length > 0)
    myElement.css(random_stuff);

answered Mar 26 '10 at 19:13

technophile

3,556
1
20
24

cool so if I wanted to "find and if cant find do nothing" how would I do this :) ? – Andrew Mar 26 '10 at 19:18

jQuery Find element else do nothing?

4 Answers4