在Angular 5中更改導航欄顏色

Question

我使用Angular 5和Bootstrap 4作為主要的前端框架。 我正在使用fixed-top引導程序的導航欄。 我在滾動窗口時試圖更改導航欄的背景。 這就是為什么我嘗試使用jquery但我遇到錯誤，即$ is not defined 。 這是我的jQuery代碼

$(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"); 
      }
    });
  });

這是我的html代碼

<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

如果將$(".navbar-fixed-top")替換$(".navbar.fixed-top") ，那么您的代碼將像以下演示一樣工作。

當jQuery庫加載失敗時，會發生$ is not defined 。 因此，您必須再次檢查您的angular-cli.json。

 $(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"); } }); }); 

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

 <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>