滚动时如何在粘性菜单中显示徽标

Question

我有一个粘性的子菜单。当我滚动到页面上的某个部分时，此菜单会粘到顶部。但是，我希望徽标显示在滚动上并在粘性菜单不在顶部时隐藏。我将如何实现？这是我想要做的一个例子（你需要在页面的一部分向下滚动以查看粘性菜单） - https://www.vidyard.com/platform/viewedit/

徽标和“获取演示”按钮是我想要实现的目标。

        var menu = document.querySelector('.menu-t')
        var menuPosition = menu.getBoundingClientRect().top;
        window.addEventListener('scroll', function () {
            if (window.pageYOffset >= menuPosition) {
                menu.style.position = 'fixed';
                menu.style.top = '0px';
            } else {
                menu.style.position = 'static';
                menu.style.top = '';
            }
        });

.page-section {
  border-bottom: 1px solid #ddd;
  overflow: hidden;
}

.page-section.page-section-center {
  align-content: center;
  text-align: center;
}


.menu-t {
  margin: 0;
  padding: 0;
  width: 100%;
  background-color: #FFF;
  z-index: 1000;
  border-bottom: 1px #eee dotted;
}
.menu-t li {
  display: inline-block;
  text-align: center;
  padding: 20px;
  text-transform: uppercase;
  font-size: 14px;
}
.menu-t a {
  display: block;
  padding: 10px 0;
  color: #32404E !important;
  -webkit-transition: color ease 0.3s;
  -o-transition: color ease 0.3s;
  transition: color ease 0.3s;
}
.menu-t a:hover {
  color: #2db2e9 !important;
}

<section class="page-section">
  <br/>
  <br/>
    <br/>
  <br/>
  </section>
<section class="page-section page-section-center hidden-xs hidden-sm">
    <ul class="menu-t">
      <li>ITEM</li>
        <li>
            <a href="#" class="text-thick">What Is</a>
        </li>
        <li>
        <a href="#" class="text-thick">How</a>
        </li>
        <li>
            <a href="#" class="text-thick">You're In Good Company</a>
        </li>
      <li>ITEM</li>
    </ul>
</section>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>

Answer 1

试试这样。

在li元素中创建一个img元素，在开始时隐藏显示并在滚动时隐藏/显示它。

var menu = document.querySelector('.menu-t')
        var menuPosition = menu.getBoundingClientRect().top;
        window.addEventListener('scroll', function () {
            if (window.pageYOffset >= menuPosition) {
                menu.style.position = 'fixed';
                menu.style.top = '0px';
                menu.firstElementChild.firstElementChild.style.display = "block";
                
            } else {
                menu.style.position = 'static';
                menu.style.top = '';
                menu.firstElementChild.firstElementChild.style.display = "none";
            }
        });

.page-section {
  border-bottom: 1px solid #ddd;
  overflow: hidden;
}

.page-section.page-section-center {
  align-content: center;
  text-align: center;
}


.menu-t {
  margin: 0;
  padding: 0;
  width: 100%;
  background-color: #FFF;
  z-index: 1000;
  border-bottom: 1px #eee dotted;
}
.menu-t li {
  display: inline-block;
  text-align: center;
  padding: 20px;
  text-transform: uppercase;
  font-size: 14px;
}
.menu-t a {
  display: block;
  padding: 10px 0;
  color: #32404E !important;
  -webkit-transition: color ease 0.3s;
  -o-transition: color ease 0.3s;
  transition: color ease 0.3s;
}
.menu-t a:hover {
  color: #2db2e9 !important;
}

.menu-t li img{
  display: none;
}

<section class="page-section">
  <br/>
  <br/>
    <br/>
  <br/>
  </section>
<section class="page-section page-section-center hidden-xs hidden-sm">
    <ul class="menu-t">
      
         <li>
            <img src="https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRJfyp7Gqe9jDGcVUgJIq0iTOOyzv6MkOthkXkAOzvqiiBPHceh"/>
        </li>
        <li>ITEM</li>
        <li>
            <a href="#" class="text-thick">What Is</a>
        </li>
        <li>
        <a href="#" class="text-thick">How</a>
        </li>
        <li>
            <a href="#" class="text-thick">You're In Good Company</a>
        </li>
      <li>ITEM</li>
    </ul>
</section>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>
  <br/>

Answer 2

示例中的徽标始终存在于导航栏中。他们使用visibility: hidden;开始，然后{滚动条贴在顶部时visibility: visible;。