javascript jQuery addClass() / removeClass() 不起作用
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jQuery addClass() / removeClass() not working
提问by fusi0n
<ul>
<li class="selected"></li>
<li></li>
<li></li>
</ul>
That is my html. And the selectors I am using right now are:
那是我的html。我现在使用的选择器是：
$("ul li:eq(0)").removeClass('selected');
$("ul li:eq(1)").addClass('selected');
Problem is that I can not add or remove the 'selected' class from these elements. The html and jquery are both pretty straight-forward and as many examples as I could find did everything the same way, including official jQuery docs. (The script is loaded before the body tag, if it matters)
问题是我无法从这些元素中添加或删除“选定”类。html 和 jquery 都非常简单，并且我能找到的尽可能多的示例都以相同的方式完成所有操作，包括官方 jQuery 文档。（脚本在 body 标签之前加载，如果重要的话）
Why can't I remove and add the classes like this?
为什么我不能像这样删除和添加类？
The entire html page here
整个html页面在这里
回答by Ahmed Alaa El-Din
probably because you forgot to add $(document).ready(),also make sure you added the jquery.min.js file
可能是因为你忘记添加了$(document).ready()，还要确保你添加了 jquery.min.js 文件
$(document).ready( function () {
$("ul li:eq(0)").removeClass('selected');
$("ul li:eq(1)").addClass('selected');
});
回答by Aaron Digulla
The code looks correct, the problem must be elsewhere. How to debug this:
代码看起来是正确的，问题一定出在别处。如何调试：
Look at how many elements the selector matches:
console.log($("ul li:eq(1)").length);If you see 0, then the selector didn't match anything.
Which element did match?
console.log($("ul li:eq(1)")[0]);Most browsers allow to examine the element in the console.
查看选择器匹配了多少元素：
console.log($("ul li:eq(1)").length);如果您看到 0，则选择器没有匹配任何内容。
哪个元素匹配？
console.log($("ul li:eq(1)")[0]);大多数浏览器允许在控制台中检查元素。
A typical problem is that your code is executed before the elements exist. In the simple case, you just need to run your code after the DOM is ready:
一个典型的问题是您的代码在元素存在之前执行。在简单的情况下，您只需要在 DOM 准备好后运行您的代码：
$(function () {
...DOM is now ready...
});
But sometimes, other scripts will create elements. If that's the case for you, you'll need to tell us which frameworks and scripts you use to build / manipulate the DOM.
但有时，其他脚本会创建元素。如果是这种情况，您需要告诉我们您使用哪些框架和脚本来构建/操作 DOM。
Related:
有关的：
回答by Orlando
$("ul li:eq(0)").removeClass('selected');
$("ul li:eq(1)").addClass('selected');
works for me (http://jsfiddle.net/orlando/rhtqA/)
对我来说有效（http://jsfiddle.net/orlando/rhtqA/）
but yeah you need to wait till DOM is ready to do stuff with jquery
但是是的，你需要等到 DOM 准备好用 jquery 做事
$(function () {
$("ul li:eq(0)").removeClass('selected');
$("ul li:eq(1)").addClass('selected');
});
