javascript - bootstrap 4 - 导航栏品牌标志在向下滚动时不会改变

Question

我添加了 bootstrap 4 并创建了导航栏，它运行良好，但我遇到了一些冲突，当向下滚动更改导航栏 Logo 时，我尝试进行更改，但它无法正常工作，任何人都知道如何解决该问题。

这是我的代码:

$(function () {
            $(window).scroll(function () {
                if ($(this).scrollTop() > 1000) {
                    $('.navbar .navbar-brand img').attr('src','https://via.placeholder.com/150/FF00FF/808080?Text=newLogo');
                }
                if ($(this).scrollTop() < 1000) {
                    $('.navbar .navbar-brand img').attr('src','https://via.placeholder.com/150/0000FF/808080?Text=oldLogo');
                }
            })
        });

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>


<header class="main_menu home_menu">
  <div class="container">
    <div class="row align-items-center">
      <div class="col-lg-12">
        <nav class="navbar navbar-expand-lg navbar-light">
          <a class="navbar-brand" > <img src="https://via.placeholder.com/150/0000FF/808080?Text=oldLogo" style="width:50px;">   </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></nav>
      </div></div></div></header>
      
      <section>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
  <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>  <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>  <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
  <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
  <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
  <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
      </section>

Answer 1

查看下面的 fiddle 。它运行良好。只是您的图像隐藏在滚动下，否则您的图像会发生变化。

请注意，出于说明目的，我修复了您的导航栏 header 。

只需为您的导航栏使用 navbar navbar-expand-lg navbar-lightfixed-top 类，它就应该按预期工作。

$(function () {
            $(window).scroll(function () {
                if ($(this).scrollTop() > 1000) {
                    $('.navbar .navbar-brand img').attr('src','https://via.placeholder.com/150/FF00FF/808080?Text=newLogo');
                }
                if ($(this).scrollTop() < 1000) {
                    $('.navbar .navbar-brand img').attr('src','https://via.placeholder.com/150/0000FF/808080?Text=oldLogo');
                }
            })
        });

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>


<header class="main_menu home_menu">
  <div class="container">
    <div class="row align-items-center">
      <div class="col-lg-12">
        <nav class="navbar navbar-expand-lg navbar-light fixed-top">
                    <a class="navbar-brand" > <img src="https://via.placeholder.com/150/0000FF/808080?Text=oldLogo" style="width:50px;">   </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></nav>
      </div></div></div></header>
      
      <section>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
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        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
        <div>Placeholder</div>
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      </section>