javascript - 滚动时隐藏 Bootstrap 导航栏

我试图在向下/向上滚动时隐藏/显示 Bootstrap 导航栏，但它似乎不起作用。我被困住了，我真的很感激这里的一些帮助。谁能告诉我我做错了什么？请记住我正在学习如何使用 Bootstrap 并且对 jQuery 知之甚少。当我使用浏览器控制台检查代码时，它没有显示任何错误。我还尝试了 fadeIn 和 fadeOut 以及 addClass 和 removeClass 函数，但没有成功。

$(document).ready(function() {

  var banner = $("#navscroll");
  $(window).scroll(function() {
    var scroll = $(window).scrollTop();
    if (scroll >= banner.height()) {
      $("#banner").hide();

    } else {
      $("banner").show();
    }
  });

});

console.log();

body {
  background-color: azure;
}

.divi {
  width: 500px;
  height: 500px;
}

#divi1 {
  background-color: red;
}

#divi2 {
  background-color: greenyellow;
}

<!DOCTYPE html>
<html lang="en">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
  <!-- Stylesheet for Mysite -->


  <title>My Site</title>

</head>

<body>

  <!-- Banner -->
  <div id="banner" class="container-fluid">
    <nav id="navscroll" class="navbar navbar-toggleable-sm navbar-light fixed-top">
      <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
      <a class="navbar-brand" href="#">My Site</a>
      <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
        <div class="navbar-nav">
          <a class="nav-item nav-link active" href="#">Me<span class="sr-only">(current)</span></a>
          <a class="nav-item nav-link" href="#">What I do</a>
          <a class="nav-item nav-link" href="#">Find Me</a>
        </div>
      </div>
    </nav>
  </div>
  <!-- Banner -->

  <!-- Divs -->
  <div class="container-fluid">
    <div id="divi1" class="divi"></div>
    <div id="divi2" class="divi"></div>
  </div>
  <!-- Divs -->



  <!-- jQuery first, then Tether, then Bootstrap JS. -->

  <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
</body>

</html>

最佳答案

有两个问题阻止您的代码在向上滚动时向后显示导航栏:

行 $("banner").show(); => banner 之前缺少“#”。
隐藏元素时，不会保留其高度。因此，在 nvarbar 隐藏后测试它的高度时，您会得到意想不到的结果。因此，我建议提前保存高度并与保存的变量进行比较。

固定代码为:

$(document).ready(function() {
  var banner_height = $("#navscroll").height();
  var lastScrollTop = 0;
  $(window).scroll(function() {
    var scroll = $(window).scrollTop();
    var currScrollTop = $(this).scrollTop();
    if (scroll >= banner_height && currScrollTop > lastScrollTop) {
      $("#banner").hide();
    } else {
      $("#banner").show();
    }
    lastScrollTop = currScrollTop;

  });

});

body {
  background-color: azure;
}

.divi {
  width: 500px;
  height: 500px;
}

#divi1 {
  background-color: red;
}

#divi2 {
  background-color: greenyellow;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<!DOCTYPE html>
<html lang="en">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
  <!-- Stylesheet for Mysite -->

  <title>My Site</title>

</head>

<body>

  <!-- Banner -->
  <div id="banner" class="container-fluid">
    <nav id="navscroll" class="navbar navbar-toggleable-sm navbar-light fixed-top">
      <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
      <a class="navbar-brand" href="#">My Site</a>
      <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
        <div class="navbar-nav">
          <a class="nav-item nav-link active" href="#">Me<span class="sr-only">(current)</span></a>
          <a class="nav-item nav-link" href="#">What I do</a>
          <a class="nav-item nav-link" href="#">Find Me</a>
        </div>
      </div>
    </nav>
  </div>
  <!-- Banner -->

  <!-- Divs -->
  <div class="container-fluid">
    <div id="divi1" class="divi"></div>
    <div id="divi2" class="divi"></div>
  </div>
  <!-- Divs -->

  <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
</body>

</html>

关于javascript - 滚动时隐藏 Bootstrap 导航栏，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45935497/

javascript - 滚动时隐藏 Bootstrap 导航栏

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