jQuery: Problems with using the first-child selector

jQuery:Usage issues of first-child

<ul>
<li>Test1<li>
<li>aaaaa<li>
<li>bbbbb<li>
</ul>

<ul>
<li>Test2<li>
<li>ccccc<li>
<li>ddddd<li>
</ul>

Use first-child to remove the

from each

For elements, using first will not work. clear?


In jQuery's child element filter selector, you need to pay attention to the use of :first-child. The example in the document is used like this:


$("ul li:first-child").addClass("highlight");


The function it implements is to obtain the first li element under all uls, which is different from:first.


$("ul li:first").addClass("highlight");


:first only gets the first li in a ul, provided that there are 2 ul lists in the page.

For:


$("ul li:first-child").addClass("highlight");

You can use another way of writing, with the same effect. Of course, I think the latter is easier to understand, because it selects the first sub-element under ul:
$("ul :first-child").addClass("highlight");
You need to pay attention to the spaces in the above examples.




$(function(){
  //$("ul li:first-child").addClass("highlight");
  //$("ul :first-child").addClass("highlight"); //和上面效果一样 注意空格
  $("ul :nth-child(2n)").addClass("highlight");
  //$(".one .mini:nth-child(2)").addClass("highlight"); //和下面一样效果
  //$(".one :nth-child(2)").addClass("highlight");
 
  //$(".one .mini:last-child").addClass("highlight"); //和下面一样效果
  $(".one :last-child)").addClass("highlight");
});

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