Uncaught TypeError: Cannot read properties of null (reading 'classList') after one click or auto-scroll in the multi-carousel

Uncaught TypeError: Cannot read properties of null (reading 'classList') after one click or auto-scroll in the multi-carousel

所以我一直在关注官方教程here and I require a slide indicator here as well so I just copied and modified the code from this example here

我的标记如下所示:

<div class="container my-5">

  <!-- Section: Introduction -->
  <section class="">

    <p>Free example of carousel with multiple items built with the newest Bootstrap 5. Learn how to create a responsive carousel with many items inside.</p>

    <p>
      Detailed documentation and more examples you can find in our
      <a href="https://mdbootstrap.com/docs/standard/components/carousel/" target="_blank"><strong>Carousel Docs</strong></a>.
    </p>
    <p>See also <a target="_blank" href="https://mdbootstrap.com/docs/standard/plugins/multi-item-carousel/"><strong>Advanced mutli item carousel plugin</strong></a>.</p>


    <hr class="mt-5">

    <p>Built with <a target="_blank" href="https://mdbootstrap.com/docs/standard/">Material Design for Bootstrap</a> - free and powerful Bootstrap UI KIT</p>

    <a class="btn btn-primary me-2" href="https://mdbootstrap.com/docs/standard/getting-started/installation/" target="_blank" role="button">Download MDB UI KIT <i class="fas fa-download ms-2"></i></a>
    <a class="btn btn-danger me-2" target="_blank" href="https://mdbootstrap.com/docs/standard/" role="button">Learn more</a>
    <a class="btn btn-success me-2" target="_blank" href="https://mdbootstrap.com/docs/standard/getting-started/" role="button">Tutorials</a>
    <a class="btn btn-dark me-2" target="_blank" href="https://github.com/mdbootstrap/mdb-ui-kit" role="button">GitHub <i class="fab fa-github ms-2"></i></a>

    <hr class="mb-5"/>

  </section>
  <!-- Section: Introduction -->

  <!-- Section: Basic example -->
  <section class="">

    <p><strong>Basic example</strong></p>

    <div class="container my-5">
      <!-- Carousel wrapper -->
      <div
           id="carouselBasicExample"
           class="carousel slide carousel-dark text-center carousel-multi-item"
           data-ride="carousel"
           data-mdb-ride="carousel"
           >
       
        <!-- Inner -->
        <div class="carousel-inner py-4">
            <ol class="carousel-indicators">
      <li data-target="#carouselBasicExample" data-slide-to="0" class="active"></li>
      <li data-target="#carouselBasicExample" data-slide-to="1"></li>
      <li data-target="#carouselBasicExample" data-slide-to="2"></li>
      <li data-target="#carouselBasicExample" data-slide-to="3"></li>
      <li data-target="#carouselBasicExample" data-slide-to="4"></li>
      <li data-target="#carouselBasicExample" data-slide-to="5"></li>
    </ol>
          <!-- Single item -->
          <div class="carousel-item active">
            <div class="container">
              <div class="row">
                <div class="col-lg-4">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/181.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/182.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/183.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>

          <!-- Single item -->
          <div class="carousel-item">
            <div class="container">
              <div class="row">
                <div class="col-lg-4 col-md-12">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/184.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.daoisjoifjoidsafpijsadpoj
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/185.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/186.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>

          <!-- Single item -->
          <div class="carousel-item">
            <div class="container">
              <div class="row">
                <div class="col-lg-4 col-md-12 mb-4 mb-lg-0">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/187.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 mb-4 mb-lg-0 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/188.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 mb-4 mb-lg-0 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/189.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
        <!-- Inner -->
      </div>
      <!-- Carousel wrapper -->
    </div>
     <!-- Controls -->
        <div class="d-flex mb-4">
          <button
                  class="carousel-control-prev justify-content-start"
                  type="button"
                  data-mdb-target="#carouselBasicExample"
                  data-mdb-slide="prev"
                  >
            <span class="carousel-control-prev-icon" aria-hidden="true">b</span>
            <span class="visually-hidden">Previous</span>
          </button>
          <button
                  class="carousel-control-next justify-content-end"
                  type="button"
                  data-mdb-target="#carouselBasicExample"
                  data-mdb-slide="next"
                  >
            <span class="carousel-control-next-icon" aria-hidden="true">a</span>
            <span class="visually-hidden">Next</span>
          </button>
        </div>

  </section>
  <!-- Section: Basic example -->
</div>

但是在 click/one 自动滚动后失败并显示错误 Uncaught TypeError: Cannot read properties of null (reading 'classList')。当你点击更多它时它不会抛出任何错误或工作,奇怪......

官方文档 (API) 在这里,但对我没有帮助:https://mdbootstrap.com/docs/standard/components/carousel/#docsTabsAPI

我将脚本包含在 HTML 内容中,它按照示例完美运行。我认为你的 HTML DOM 树中缺少某些东西,这使得你的代码停在这里 Uncaught TypeError: Cannot read properties of null (reading 'classList')

它可能是结束语 div,因此这就是为什么您的 carousel.js 中断并且无法继续下一张幻灯片的原因。通过一些调试,我实际上找到了它,但是为了访问 classList 的 属性,你必须像这样放置它 classList[0],通常不应该有这个结构。它必须是简单的 classList.remove(YOUR_CLASS)

您应该在此文件夹内设置一个断点,以获取您实际需要的信息。

<link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.0.0/css/all.min.css" rel="stylesheet"/>
<link href="https://cdnjs.cloudflare.com/ajax/libs/mdb-ui-kit/3.11.0/mdb.min.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mdb-ui-kit/3.11.0/mdb.min.js"></script>


<div class="container my-5">

  <!-- Section: Introduction -->
  <section class="">

    <p>Free example of carousel with multiple items built with the newest Bootstrap 5. Learn how to create a responsive carousel with many items inside.</p>

    <p>
      Detailed documentation and more examples you can find in our
      <a href="https://mdbootstrap.com/docs/standard/components/carousel/" target="_blank"><strong>Carousel Docs</strong></a>.
    </p>
    <p>See also <a target="_blank" href="https://mdbootstrap.com/docs/standard/plugins/multi-item-carousel/"><strong>Advanced mutli item carousel plugin</strong></a>.</p>


    <hr class="mt-5">

    <p>Built with <a target="_blank" href="https://mdbootstrap.com/docs/standard/">Material Design for Bootstrap</a> - free and powerful Bootstrap UI KIT</p>

    <a class="btn btn-primary me-2" href="https://mdbootstrap.com/docs/standard/getting-started/installation/" target="_blank" role="button">Download MDB UI KIT <i class="fas fa-download ms-2"></i></a>
    <a class="btn btn-danger me-2" target="_blank" href="https://mdbootstrap.com/docs/standard/" role="button">Learn more</a>
    <a class="btn btn-success me-2" target="_blank" href="https://mdbootstrap.com/docs/standard/getting-started/" role="button">Tutorials</a>
    <a class="btn btn-dark me-2" target="_blank" href="https://github.com/mdbootstrap/mdb-ui-kit" role="button">GitHub <i class="fab fa-github ms-2"></i></a>

    <hr class="mb-5"/>

  </section>
  <!-- Section: Introduction -->

  <!-- Section: Basic example -->
  <section class="">

    <p><strong>Basic example</strong></p>

    <div class="container my-5">
      <!-- Carousel wrapper -->
      <div
           id="carouselBasicExample"
           class="carousel slide carousel-dark text-center"
           data-mdb-ride="carousel"
           >
        <!-- Controls -->
        <div class="d-flex justify-content-center mb-4">
          <button
                  class="carousel-control-prev position-relative"
                  type="button"
                  data-mdb-target="#carouselBasicExample"
                  data-mdb-slide="prev"
                  >
            <span class="carousel-control-prev-icon" aria-hidden="true"></span>
            <span class="visually-hidden">Previous</span>
          </button>
          <button
                  class="carousel-control-next position-relative"
                  type="button"
                  data-mdb-target="#carouselBasicExample"
                  data-mdb-slide="next"
                  >
            <span class="carousel-control-next-icon" aria-hidden="true"></span>
            <span class="visually-hidden">Next</span>
          </button>
        </div>
        <!-- Inner -->
        <div class="carousel-inner py-4">
          <!-- Single item -->
          <div class="carousel-item active">
            <div class="container">
              <div class="row">
                <div class="col-lg-4">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/181.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/182.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/183.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>

          <!-- Single item -->
          <div class="carousel-item">
            <div class="container">
              <div class="row">
                <div class="col-lg-4 col-md-12">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/184.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/185.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/186.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>

          <!-- Single item -->
          <div class="carousel-item">
            <div class="container">
              <div class="row">
                <div class="col-lg-4 col-md-12 mb-4 mb-lg-0">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/187.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 mb-4 mb-lg-0 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/188.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>

                <div class="col-lg-4 mb-4 mb-lg-0 d-none d-lg-block">
                  <div class="card">
                    <img
                         src="https://mdbootstrap.com/img/new/standard/nature/189.jpg"
                         class="card-img-top"
                         alt="..."
                         />
                    <div class="card-body">
                      <h5 class="card-title">Card title</h5>
                      <p class="card-text">
                        Some quick example text to build on the card title and
                        make up the bulk of the card's content.
                      </p>
                      <a href="#!" class="btn btn-primary">Button</a>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
      <!-- Carousel wrapper -->
    </div>
     <!-- Controls -->
        <div class="d-flex mb-4">
          <button
                  class="carousel-control-prev justify-content-start"
                  type="button"
                  data-mdb-target="#carouselBasicExample"
                  data-mdb-slide="prev"
                  >
            <span class="carousel-control-prev-icon" aria-hidden="true">b</span>
            <span class="visually-hidden">Previous</span>
          </button>
          <button
                  class="carousel-control-next justify-content-end"
                  type="button"
                  data-mdb-target="#carouselBasicExample"
                  data-mdb-slide="next"
                  >
            <span class="carousel-control-next-icon" aria-hidden="true">a</span>
            <span class="visually-hidden">Next</span>
          </button>
        </div>

  </section>
  <!-- Section: Basic example -->
</div>