javascript - JQUERY 在多个无序列表中选择第 n 个列表元素

Question

不幸的是，这不能用纯 css 来完成，因为 nth-of-type 只选择与元素的父元素 (w3schools) 的关系。所以我正在寻找适用于多个列表的 jquery 替代方案。

HTML:

<div class="container" id="videos">
   <ul class="thumbnails">
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
   </ul>
   <ul class="thumbnails">
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
   </ul>
   <ul class="thumbnails">
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
      <li class="tn">
         <img class="tn-img" src="img/thumbnails/placeholder.jpg" />
      </li>
   </ul>
</div>

JQUERY

$( "#videos li:nth-of-type(5n+1) img" ).css( "margin-left" , "0px");

此代码仍在选择 :nth-of-type(5n+1) 与其父级(无序列表)相关。我知道是因为每个 ul 中的第一个列表项都被选中了。我需要在每个无序列表中选择第 5 个列表项，而不管它的父项。

Answer 1

var items = $('#videos li'),
    counter = 0, // first element, counting starts at zero
    step = 5,
    item = null;

while((item = items.eq(counter)).length) {
    item.addClass('special'); // or do whatever else with it
    counter += step;
}

http://jsfiddle.net/1573ahug/

---

编辑:或者，通过一个很好的 ol' for 循环(这样我们就不必经常调用 .length 来查看是否还有元素):

var items = $('#videos li'),
    start = 0, // first element, counting starts at zero
    step = 5;

for(var i=start, l=items.length; i<l; i+=step) {
    items.eq(i).addClass('special');
}

http://jsfiddle.net/1573ahug/1/