$("ul li:nth-child(2)").append(" - 2nd!");nth-child(2)什么意思？？？

[plglenn15]

nth-child(2)什么意思？？？

http://docs.jquery.com/Selectors/nthChild#index
Selectors/nthChild
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:nth-child(index/even/odd/equation)

* Overview
* Examples

Matches all elements that are the nth-child of their parent or that are the parent's even or odd children.
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.

    * Demo
    * View Source

Finds the second li in each matched ul and notes it.

$("ul li:nth-child(2)").append("<span> - 2nd!</span>");

[qqzeng-ip]

在每个 ul 查找第 2 个li

[wuyq11]

nth-child(n) 返回第n个子元素. 如：li:nth-child(2) 返回 所有作为子元素的 li 项的第二个.
:nth-child(even|odd) 返回偶数(Even) 或奇数(Odd) 子元素. 如：li:nth-child(even) 返回所有作为子元素的li项的偶数元素.
:nth-child(Xn+Y) 返回Xn+Y计算结果的第n个子元素.如果Y为0，则被忽略. 如：li:nth-child(3n) 返回所有作为子元素的li项的每第3n个元素

[qqzeng-ip]

<ul>
  <li>John</li>
  <li>Karl</li>
  <li>Brandon</li>
</ul>
<ul>
  <li>Glen</li>
  <li>Tane</li>
  <li>Ralph</li>
</ul>

$("ul li:nth-child(2)")

结果:

<li>Karl</li>,   <li>Tane</li> 

[chen_ya_ping]

建议楼主下载一份jquery的文档，上面有很详细的解释。或者网上还有电子书的。这个是代表的这个节点下的第2个子节点，那个n是从1开始的。其他的地方都是从0开始。