选择第j个前面的兄弟姐妹？ [英] Select Nth previous sibling in jQuery?

问题描述

我尝试设置我的jQuery选择器，但我不知道我需要如何写它。

我有一个无序的列表看起来像这样：

 < ul> 
< li>某事< / li> 
< li>某事< / li> 
< li>某事< / li> 
< li>某事< / li> 
< li class =last> something< / li> 
< / ul> 
  

现在我知道如果我想选择最后一个孩子， .last或ul.li:last，但是如果我想要从最后一秒，第三或第20秒？

解决方案

您可以使用 eq ：

  $（'ul li'）。eq（X）; 
  

其中X是您想要的元素的基于0的索引。您还可以使用选择器表单：

  $（'ul li：eq（X）'）; 
  

您也可以使用 nth-child ：

  $（'ul li：nth-​​child（X）'）; 
  

本文档介绍了 nth-child 和 eq ：

While：eq只有一个元素，这匹配多个：每个父索引一个。每个父项具有偶数，奇数或方程的倍数。指定的索引是单索引的，相比之下：eq（）从零开始。

c> $（'ul li'）。eq（19）; 您将获得查询的第20个匹配元素（因此，如果文档中有多个列表，你的所有第19个孩子，而 $（'ul li：nth-​​child（20）'）; 会得到你个人的第20个匹配的列表元素<$ c

$ b

要做类似秒到末尾的操作，那么这样做的正确方法是：

  var $ ul = $（'＃mylist> li'）; 
 var $ el = $ ul.eq（$ ul.length-2）; 
  pre> 
 
 
但你应该检查一下，确保length-2不小于0. 
 
I'm trying to set up my jQuery selector but I'm not exactly sure how I need to write it.

I've got a unordered list that looks something like this:
<ul>
    <li>something</li>
    <li>something</li>
    <li>something</li>
    <li>something</li>
    <li class="last">something</li>
</ul>
Now I know if I want to select the last child I can do that by using either "ul li.last" or "ul.li:last" but say if I wanted the second from last, or third, or 20th? Now would I do that?
解决方案
You use eq:
$('ul li').eq(X);
Where X is a 0-based index of which element you want. You could also use the selector form:
$('ul li:eq(X)');
And you could also achieve a similar result by using nth-child:
$('ul li:nth-child(X)');
The documentation has this to say about the difference between nth-child and eq:

  
While :eq(index) matches only a single element, this matches more than one: One for each parent with index. Multiple for each parent with even, odd, or equation. The specified index is one-indexed, in contrast to :eq() which starts at zero.
So by doing $('ul li').eq(19); you would get the single 20th matched element of the query (so if there is more than one list in the document this won't get you "all 19th children", while $('ul li:nth-child(20)'); would get you the individual 20th matched list element of each <ul> in the document.

EDIT:

To do something like "second to last", the sane way to do it would be like:
var $ul = $('#mylist > li');
var $el = $ul.eq($ul.length-2);
But you should probably do a check to make sure length-2 is not less than 0.

                        
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