:nth-of-type() in jQuery / Sizzle?

Asked 19/1, 2010 at 12:20 Answered 21/1, 2011 at 16:58

Solved jquery jquery-selectors css-selectors selectors-api

It surprised me that Sizzle (the selector engine jQuery uses) comes with a built-in :nth-child() selector, but lacks an :nth-of-type() selector.

To illustrate the difference between :nth-child() and :nth-of-type() and to illustrate the problem, consider the following HTML document:

<!doctype html>
<html>
 <head>
  <meta charset="utf-8">
  <title>:nth-of-type() in Sizzle/jQuery?</title>
  <style>
   body p:nth-of-type(2n) { background: red; }
  </style>
 </head>
 <body>
  <p>The following CSS is applied to this document:</p>
  <pre>body p:nth-of-type(2n) { background: red; }</pre>
  <p>This is paragraph #1.</p>
  <p>This is paragraph #2. (Should be matched.)</p>
  <p>This is paragraph #3.</p>
  <p>This is paragraph #4. (Should be matched.)</p>
  <div>This is not a paragraph, but a <code>div</code>.</div>
  <p>This is paragraph #5.</p>
  <p>This is paragraph #6. (Should be matched.)</p>
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
  <script>
   $(function() {
    // The following should give every second paragraph (those that had red backgrounds already after the CSS was applied) an orange background.
    // $('body p:nth-of-type(2n)').css('background', 'orange');
   });
  </script>
 </body>
</html>

Since Sizzle uses the browser-native querySelector() and querySelectorAll() methods if those are present (i.e. in browsers that already implement the Selectors API), stuff like $('body p:nth-child'); will of course work. It won’t work in older browsers though, because Sizzle has no fallback method for this selector.

Is it possible to easily add the :nth-of-type() selector to Sizzle, or to implement it in jQuery (by using the built-in :nth-child() selector, perhaps)? A custom selector with parameters would be nice.

Nieves answered 19/1, 2010 at 12:20 Comment(8)

Not sure, but won't $('p:even') give you what you're looking for? You already have the selector (p), so you just need to filter it. – Radiolocation 19/1, 2010 at 13:19

@Kobi: It’s not that easy. The selector p:nth-child(2n) would match every second paragraph in every parent element. If there are two DIVs, both containing three paragraphs, the following paragraphs (in DOM order) would be matched by p:nth-child(2n): #2, #5. See? It’s not just a matter of getting every P in the document and then filtering it down to every mnth elementh. Yes, $('p:even') is an alias for $('p:nth-child(2n)'), but not for $('p:nth-of-type(2n)'). Also, I’m using 2n in this example, but of course other variations should be possible as well. – Nieves 19/1, 2010 at 13:28

Got it, and deleted my answer. – Radiolocation 19/1, 2010 at 13:32

$('body p:nth-of-type(n)').css('background', 'orange'); is working in firefox here on jQuery 1.4, are you asking how to implement this strictly for older browsers, e.g. implement only the fallback version? – Municipalize 19/1, 2010 at 22:36

Nick Craver, like I explained in my post, that’s because Firefox is one of the browsers with a native implementation of the Selectors API. Sizzle doesn’t know the :nth-of-type() selector, but Firefox’s querySelectorAll() does. That’s why it ‘works’ — but it’s not thanks to Sizzle. It would be good to have this in Sizzle because then it would work in all browsers. – Nieves 20/1, 2010 at 9:55

Sorry, can you elaborate on why $('body p:nth-child') does not work in older browsers? Because that's your only argument against using it, right? – Grandparent 20/1, 2010 at 16:59

littlegreen: $('body p:nth-child') works in every browser, because Sizzle has a built-in :nth-child() selector. So, if the browser doesn’t implement the Selectors API, Sizzle just uses that instead. The problem is Sizzle lacks an :nth-of-type() selector. – Nieves 21/1, 2010 at 9:56

Wouldn't you know it, it wasn't implemented simply because John Resig didn't think it was worth implementing. – Alixaliza 1/3, 2012 at 7:26

/**
 * Return true to include current element
 * Return false to exclude current element
 */
$.expr[':']['nth-of-type'] = function(elem, i, match) {
    if (match[3].indexOf("n") === -1) return i + 1 == match[3];
    var parts = match[3].split("+");
    return (i + 1 - (parts[1] || 0)) % parseInt(parts[0], 10) === 0;
};

Test case - (check in IE or rename the selector)

You can of course add even & odd too:

match[3] = match[3] == "even" ? "2n" : match[3] == "odd" ? "2n+1" : match[3];

Yakutsk answered 21/1, 2011 at 16:58 Comment(3)

Cool! This is what I was looking for; a short, clever, concise, solution. As you know, :odd and :even are already supported in jQuery, just not in the :nth-of-type(odd) / :nth-of-type(even) form, but it’s nice to have ’em in there as well for the sake of completeness. – Nieves 25/1, 2011 at 8:5

Update: for even more selectors, see github.com/keithclark/JQuery-Extended-Selectors – Nieves 30/3, 2011 at 16:40

Nice, but i just wanted to warn others about this solution always assuming a periodicity (n). I mean, filter like :nth-of-type(2n) and :nth-of-type(2) will be the same (when the latter should only be the 2nd element, instead of all the even elements). – Telfer 18/5, 2011 at 21:12

the jQuery plugin moreSelectors has support for nth-of-type (and many other selectors). I suggest either using that, or simply implement a simple plugin that only implements the exact selectors you need. You should be able to copy-paste code from there.

Happy hacking!

Apportion answered 22/1, 2010 at 16:21 Comment(0)

I can't pretend to know how nth-of-type is implemented, but jQuery does provide a mechanism by which you can create your own custom selector.

The following question deals with custom selectors, and may provide a useful insight to you

What useful custom jQuery selectors have you written?

Imperishable answered 19/1, 2010 at 13:29 Comment(1)

Yes, I am aware of this… I should probably add that to my post. – Nieves 19/1, 2010 at 13:43

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