JQuery CSS select first & last LI form UL list

looking for some help please with the JQuery CSS selector. I want to identify the first and last LI from the main UL list and alter the CSS class. The 开发者_JAVA百科first should be class="grid_4 alpha" and the last class="grid_4 omega"

<ul>
    <li id="linkcat-2" class="grid_4 this should be alpha"><h4 class="widgettitle">Blogroll</h4>
     <ul class='xoxo blogroll'>
      <li><a href="http://wordpress.com/">WordPress.com</a></li>
      <li><a href="http://wordpress.org/">WordPress.org</a></li>
     </ul>
</li>
<li id="linkcat-2" class="grid_4"><h4 class="widgettitle">Blogroll</h4>
 <ul class='xoxo blogroll'>
  <li><a href="http://wordpress.com/">WordPress.com</a></li>
  <li><a href="http://wordpress.org/">WordPress.org</a></li>
 </ul>
</li>
<li id="linkcat-2" class="grid_4"><h4 class="widgettitle">Blogroll</h4>
 <ul class='xoxo blogroll'>
  <li><a href="http://wordpress.com/">WordPress.com</a></li>
  <li><a href="http://wordpress.org/">WordPress.org</a></li>
 </ul>
</li>
<li id="linkcat-2" class="grid_4 this should be omega"><h4 class="widgettitle">Blogroll</h4>
 <ul class='xoxo blogroll'>
  <li><a href="http://wordpress.com/">WordPress.com</a></li>
  <li><a href="http://wordpress.org/">WordPress.org</a></li>
 </ul>
</li>
</ul>

I just cannot get the right JQuery.css functio to work.

Help much appreciated - I can add an id to the master ul if requyired

Use :first-child and :last-child with the child (>) selector:

$("#master > :first-child").addClass("grid_4 alpha");
$("#master > :last-child").addClass("grid_4 omega");

Bear in mind that classes can't have spaces in them. This markup:

<li class="grid_4 alpha">...

defines a list element that has two classes. If you want to select it you can use:

$("li.grid_4.alpha")...

meaning select all the list elements that have both the grid_4 and alpha classes.

You should use the following selectors:

http://api.jquery.com/first-selector/

http://api.jquery.com/last-selector/

e.g.:

$("ul li:first").addClass("alpha");
$("ul li:last").addClass("omega");

$('ul > li:first').addClass('alpha');
$('ul > li:last').addClass('omega');

Hey remember the end of Beneath The Planet Of The Apes? That was pretty cool, with the big bomb and everything. Oops I hope I didn't give it away for anybody!

How about this:

$('ul li:first').addClass('alpha');
$('ul li:last').addClass('omage');

Hope this helps :)

One thing that may cause you a problem in your example is that you have assigned the same id to many items:

id="linkcat-2"

The id is supposed to be unique.

However, this is how you select first and last:

<ul id="main">
    <li>One</li>
    <li>Two
        <ul>
            <li>Two A</li>
            <li>Two B</li>
        </ul>
    </li>
    <li>Three</li>
    <li>Four
        <ul>
            <li>Two A</li>
            <li>Two B</li>
        </ul>
    </li>
</ul>

<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript">
    alert($("#main > :first-child").text());
    alert($("#main > :last-child").text());
</script>