Question

＆＃13;

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
  
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
</head>
<body>
	<div id="carousel-example-generic" class="carousel slide" data-ride="carousel">
  <!-- Indicators -->
  <ol class="carousel-indicators">
    <li data-target="#carousel-example-generic" data-slide-to="0" class="active"></li>
    <li data-target="#carousel-example-generic" data-slide-to="1"></li>
    <li data-target="#carousel-example-generic" data-slide-to="2"></li>
  </ol>

  <!-- Wrapper for slides -->
  <div class="carousel-inner" role="listbox">
    <div class="item active">
      <img src="http://ichef.bbci.co.uk/news/976/cpsprodpb/87D3/production/_84817743_beckhamfashion.jpg" alt="...">
      <div class="carousel-caption">
        ...
      </div>
    </div>
    <div class="item">
      <img src="http://ichef.bbci.co.uk/news/976/cpsprodpb/9949/production/_84814293_dummy.jpg" alt="...">
      <div class="carousel-caption">
        ...
      </div>
    </div>
    ...
  </div>

  <!-- Controls -->
  <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
    <span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
    <span class="sr-only">Previous</span>
  </a>
  <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
    <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
    <span class="sr-only">Next</span>
  </a>
</div>
  
  
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>

<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
</body>
</html>

＆＃13;

我使用bootstap carousel作为例子;

<div id="carousel-example-generic" class="carousel slide" data-ride="carousel">

  <div class="carousel-inner" role="listbox">

    <div class="item active">
      <img src="..." alt="...">
      <div class="carousel-caption">

      </div>
    </div>

    <div class="item">
      <img src="..." alt="...">
      <div class="carousel-caption">
        ...
      </div>
    </div>

  </div>

  <!-- Controls -->
  <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
    <span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
    <span class="sr-only">Previous</span>
  </a>
  <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
    <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
    <span class="sr-only">Next</span>
  </a>
</div>

正如您所看到的，我的第一个.item班级有.active课程，但是当我从.active课程中删除.item课程时，我想自动添加它，然后javascript给了我这个错误：TypeError: Cannot read property 'offsetWidth' of undefined /works/anitur/js/bootstrap.min.js:6我尝试使用此代码添加

$(".carousel > .item:first").addClass("active");

但没有什么改变我怎么才能意识到自己想要什么呢？顺便说一下，有没有办法用js而不是html添加轮播控件？

Answer 1

最好在HTML模板本身中为旋转木马添加类。为什么因为轮播插件会在document is ready之后重建HTML。但是，您可以尝试以下代码。

$(".carousel .item").first().addClass("active");

Answer 2

你应该纠正这个 $(".carousel .item:first").addClass("active");

Answer 3

我已逐一尝试过，这段代码是为第一项元素添加活动类的正确代码

$(".carousel .item:first").addClass("active");

有关详细信息，请参阅图片中的红色框和箭头您也可以在实时版本中查看它，

为第一个项目元素添加活动类

3 个答案: