jquery - 悬停导航栏时如何使网页变暗，就像引导模式一样？

Question

是否可以使用 Bootstrap 在模态打开时使页面变暗时使用的相同过程？

我希望它能在我将鼠标悬停在引导导航栏上时使页面变暗。
当然，我不希望导航栏变暗!

modal-dim 是如何工作的？
我可以使用相同的 css 吗？

Answer 1

您可以使用所有主流浏览器都支持的纯 CSS 来做到这一点。

.navbar:hover+.nav-sibling {
  display: block;
  opacity: 0.5;
  background: rgba(0, 0, 0, 1);
  transition: opacity .15s linear;
}

.nav-sibling {
  position: fixed;
  display: none;
  overflow: hidden;
  outline: 0;
  /* equal to the navbar height */
  top: 56px;
  bottom: 0;
  left: 0;
  right: 0;
}

<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.1/css/bootstrap.css" rel="stylesheet" />
<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>

  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Link</a>
      </li>
      <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
              Dropdown
            </a>
        <div class="dropdown-menu" aria-labelledby="navbarDropdown">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="#">Something else here</a>
        </div>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
      <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>
<div class="nav-sibling">

</div>
<footer class=" container-fluid bg-dark text-white py-5">
  <div class="row">
    <div class="col-12">
      <h6>Lorem ipsum</h6>
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam eget sapien dolor. Nam aliquam augue ante, et sodales felis vulputate iaculis.</p>
    </div>
  </div>
</footer>

nav-sibling 除了 top 属性外，与引导模态代码相同。

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更新

Opacity sets the opacity value for an element and all of its children; While RGBA sets the opacity value only for a single declaration. - StackOverflow - opacity vs RGBA

最好为 alpha channel 使用 0 和 1 之间的数字，而不是 不透明度。在下面的代码中，我使用了 0.9。

.navbar:hover+.nav-sibling {
  display: block;
  background-color: rgba(0, 0, 0, 0.9);
  transition: all .15s linear;
}