滚动时导航栏更改，无法使用库

Question

我试图让我的导航栏从透明滚动后变成纯色。我看了一些例子，但是他们正在使用我无法使用的bootstrap / libraries。我尝试过使用JS，但我无法进行任何更改。我的代码如下：

var myNav = document.getElementById('mynav');
window.onscroll = function() {

  if (document.body.scrollTop >= 200) {
    myNav.classList.add("nav-bar");
    myNav.classList.remove("navtransparent");
  } else {
    myNav.classList.add("navtransparent");
    myNav.classList.remove("nav-bar");
  }
};

.nav-bar {
  position: fixed;
  z-index: 9999;
  top: 0;
  width: 100%;
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  border: 1px solid #696969;
  background-color: #c0c0c0;
}

.navtransparent {
  background-color: transparent;
}

li.navlist {
  float: right;
}

li.navlist a {
  display: block;
  padding: 6px;
  padding-left: 10px;
  padding-right: 10px;
  text-align: 14px 16px;
  text-decoration: none;
  color: #4d4d4d;
}

li.navlist:hover a {
  background-color: #d3d3d3;
}

<nav div='mynav'>
  <ul class="nav-bar">
    <li class="navlist"><a href="#four">E</a></li>
    <li class="navlist"><a href='#three'>D</a></li>
    <li class="navlist"><a href='#two'>C</a></li>
    <li class="navlist"><a href='#one'>B</a></li>
    <li class="navlist"><a href='#home'>A</a></li>
  </ul>
</nav>

Answer 1

主要问题（修复id 后的）是.nav-bar上已有ul类，这可以解决这个问题。一开始。

因此，将ul的样式和固定#mynav的样式分解为不同的规则。

您还需要检查document.body.scrollTop和document.documentElement.scrollTop，因为有些浏览器会滚动html而其他浏览器会滚动body。

var myNav = document.getElementById('mynav');
window.onscroll = function() {
  var scroll = document.body.scrollTop || document.documentElement.scrollTop;
  
  if (scroll >= 50) {
    myNav.classList.add("navfixed");
    myNav.classList.remove("navtransparent");
  } else {
    myNav.classList.add("navtransparent");
    myNav.classList.remove("navfixed");
  }
};

.nav-bar {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
}
.navfixed{
  position:fixed;
  z-index: 9999;
  top: 0;
  width: 100%;
  left:0;
  background-color: #c0c0c0;
  border: 1px solid #696969;
}
.navtransparent {
  background-color: transparent;
}

li.navlist {
  float: right;
}

li.navlist a {
  display: block;
  padding: 6px;
  padding-left: 10px;
  padding-right: 10px;
  text-align: 14px 16px;
  text-decoration: none;
  color: #4d4d4d;
}

li.navlist:hover a {
  background-color: #d3d3d3;
}

<nav id='mynav'>
  <ul class="nav-bar">
    <li class="navlist"><a href="#four">E</a></li>
    <li class="navlist"><a href='#three'>D</a></li>
    <li class="navlist"><a href='#two'>C</a></li>
    <li class="navlist"><a href='#one'>B</a></li>
    <li class="navlist"><a href='#home'>A</a></li>
  </ul>
</nav>

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