Question

我使用Angular 5和Bootstrap 4作为我的主要前端框架。我正在使用fixed-top bootstrap的导航栏。我正在尝试在滚动窗口时更改导航栏的背景。这就是为什么我尝试使用jquery但我收到错误，即$ is not defined。这是我的jquery代码

$(document).ready(function(){
    $(window).scroll(function() { 
      if ($(document).scrollTop() > 50) { 
        $(".navbar-fixed-top").css("background-color", "#ffffff");
      } else {
        $(".navbar-fixed-top").css("background-color", "transparent"); 
      }
    });
  });

这是我的HTML代码

<nav class="navbar navbar-expand-lg fixed-top navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarColor03" aria-controls="navbarColor03" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarColor03">
    <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="#">Features</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Pricing</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">About</a>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="text" placeholder="Search">
      <button class="btn btn-secondary my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>

Answer 1

如果您将$(".navbar-fixed-top")替换为$(".navbar.fixed-top")，那么您的代码就像下面的演示一样。

当jQuery库加载失败时，会出现

$ is not defined。所以你必须再次检查你的angular-cli.json。

＆＃13;

$(document).ready(function(){
    $(window).scroll(function() { 
      if ($(document).scrollTop() > 50) { 
        // change the color from white to red to show the effect
        $(".navbar.fixed-top").css("background-color", "red");
      } else {
        $(".navbar.fixed-top").css("background-color", "transparent"); 
      }
    });
  });

＆＃13;

nav{
  height: 200vh; /* increase the height to make it scrollable*/
}

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<nav class="navbar navbar-expand-lg fixed-top navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarColor03" aria-controls="navbarColor03" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarColor03">
    <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="#">Features</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Pricing</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">About</a>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="text" placeholder="Search">
      <button class="btn btn-secondary my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>

＆＃13;

改变角度5中的导航栏颜色

1 个答案: