粘性响应式移动汉堡菜单不会显示

Question

我有一个粘滞响应式移动汉堡菜单，如果我在页面顶部，则必须单击两次以使其下推文本，然后将其打开。当我滚动并停在中间页的某个位置并尝试将其打开时，整个topnav栏将消失，并在我开始滚动时再次返回，但它从未展开以显示其他链接。

<script>
function responsive() {
    var x = document.getElementById("myTopnav");
    if (x.className === "topnav") {
        x.className += " responsive";
    } else {
        x.className = "topnav";
    }
}

</script>

<script>
// When the user scrolls the page, execute myFunction
window.onscroll = function() {myFunction()};

// Get the myTopnav
var myTopnav = document.getElementById("myTopnav");

// Get the offset position of the myTopnav
var sticky = myTopnav.offsetTop;

// Add the sticky class to the myTopnav when you reach its scroll position. Remove "sticky" when you leave the scroll position
function myFunction() {
  if (window.pageYOffset >= sticky) {
    myTopnav.classList.add("sticky")
  } else {
    myTopnav.classList.remove("sticky");
  }
}
</script>

.sticky {
  position: fixed;
  top: 0;
  width: 100%;
  z-index: 5;


}
.topnav {
    background-color: #005E7B ;
    overflow: hidden;
	z-index: 5;
	font-weight: bold;
	
}

/* Style the links inside the navigation bar */
.topnav a {
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    padding: 0.875em 1em;
    text-decoration: none;
    font-size: 1.0625em;

}

/* Hide the link that should open and close the topnav on small screens */
.topnav .icon {
    display: none;
}

/* Dropdown container - needed to position the dropdown content */
.dropdown {
    float: left;
    overflow: hidden;
}

/* Style the dropdown button to fit inside the topnav */
.dropdown .dropbtn {
    font-size: 1.0625em; 
    border: none;
    outline: none;
    color: white;
    padding: 0.875em 1em;
    background-color: inherit;
    font-family: inherit;
    margin: 0;
}

/* Style the dropdown content (hidden by default) */
.dropdown-content {
    display: none;
    position: fixed;
    background-color: #f9f9f9;
    min-width: 10em;
    box-shadow: 0px 0.5em 1em 0px rgba(0,0,0,0.2);
    z-index: 1;
	font-weight: normal;
}

/* Style the links inside the dropdown */
.dropdown-content a {
    float: none;
    color: black;
    padding: 0.75em 1em;
    text-decoration: none;
    display: block;
    text-align: left;
	
}

@media screen and (max-width: 600px) {
	

  .topnav a:not(:first-child), .dropdown .dropbtn {
    display: none;
  }
  .topnav a.icon {
    float: right;
    display: block;
  }

.topnav.responsive {
	position: fixed;
	display: block;
	width:100%;
	z-index:999;
}
  .topnav.responsive a.icon {
    position: absolute;
    right: 0;
    top: 0;
  }
  .topnav.responsive a {
    float: none;
    display: block;
    text-align: left;
  }
  .topnav.responsive .dropdown {float: none;}
  .topnav.responsive .dropdown-content {position: relative;}
  .topnav.responsive .dropdown .dropbtn {
    display: block;
    width: 100%;
    text-align: left;
  }

<nav>
<div class="topnav" id="myTopnav">
  <a href="#about">About me</a>
    <div class="dropdown">
    <div class="dropbtn">Example
    </div>
    <div class="dropdown-content">
      <a href="#Example">Example</a>
      <a href="#Example">Example</a>
      <a href="#Example">Example</a>
	  <a href="#Example">Example</a>
	  <a href="#Example">Example</a>
    </div>
  </div>
  <a href="#Example">Example</a>
  <a href="#about">Example</a>
  <a href="#about">Example</a>
  <a href="javascript:void(0);" class="icon" onclick="responsive()">&#9776;</a>
</div>
</nav>

Answer 1

您的所有HTML，CSS和JS都是正确的，您在responsive()函数中犯了一个小错误，即您在导航上错误地切换了.responsive类，我在下面对此进行了修复：

function responsive() {
  var x = document.getElementById("myTopnav");
  x.classList.toggle('responsive');
}

// When the user scrolls the page, execute myFunction
window.onscroll = function() {myFunction()};

// Get the myTopnav
var myTopnav = document.getElementById("myTopnav");

// Get the offset position of the myTopnav
var sticky = myTopnav.offsetTop;

// Add the sticky class to the myTopnav when you reach its scroll position. Remove "sticky" when you leave the scroll position
function myFunction() {
  if (window.pageYOffset >= sticky) {
    myTopnav.classList.add("sticky")
  } else {
    myTopnav.classList.remove("sticky");
  }
}

body {
  /* added long height to body so that it's scrollable */
  height: 800px;
}

.sticky {
  position: fixed;
  top: 0;
  width: 100%;
  z-index: 5;
}

.topnav {
  background-color: #005E7B ;
  overflow: hidden;
	z-index: 5;
	font-weight: bold;
}

/* Style the links inside the navigation bar */
.topnav a {
  float: left;
  display: block;
  color: #f2f2f2;
  text-align: center;
  padding: 0.875em 1em;
  text-decoration: none;
  font-size: 1.0625em;
}

/* Hide the link that should open and close the topnav on small screens */
.topnav .icon {
  display: none;
}

/* Dropdown container - needed to position the dropdown content */
.dropdown {
  float: left;
  overflow: hidden;
}

/* Style the dropdown button to fit inside the topnav */
.dropdown .dropbtn {
  font-size: 1.0625em; 
  border: none;
  outline: none;
  color: white;
  padding: 0.875em 1em;
  background-color: inherit;
  font-family: inherit;
  margin: 0;
}

/* Style the dropdown content (hidden by default) */
.dropdown-content {
  display: none;
  position: fixed;
  background-color: #f9f9f9;
  min-width: 10em;
  box-shadow: 0px 0.5em 1em 0px rgba(0,0,0,0.2);
  z-index: 1;
	font-weight: normal;
}

/* Style the links inside the dropdown */
.dropdown-content a {
  float: none;
  color: black;
  padding: 0.75em 1em;
  text-decoration: none;
  display: block;
  text-align: left;
}

@media screen and (max-width: 600px) {
  .topnav a:not(:first-child),
  .dropdown .dropbtn {
    display: none;
  }
  
  .topnav a.icon {
    float: right;
    display: block;
  }

  .topnav.responsive {
  	position: fixed;
  	display: block;
  	width:100%;
  	z-index:999;
  }
  
  .topnav.responsive a.icon {
    position: absolute;
    right: 0;
    top: 0;
  }
  
  .topnav.responsive a {
    float: none;
    display: block;
    text-align: left;
  }
  
  .topnav.responsive .dropdown {
    float: none;
  }
  
  .topnav.responsive .dropdown-content {
    position: relative;
  }
  
  .topnav.responsive .dropdown .dropbtn {
    display: block;
    width: 100%;
    text-align: left;
  }
}

<nav>
<div class="topnav" id="myTopnav">
  <a href="#about">About me</a>
    <div class="dropdown">
    <div class="dropbtn">Example
    </div>
    <div class="dropdown-content">
      <a href="#Example">Example</a>
      <a href="#Example">Example</a>
      <a href="#Example">Example</a>
	  <a href="#Example">Example</a>
	  <a href="#Example">Example</a>
    </div>
  </div>
  <a href="#Example">Example</a>
  <a href="#about">Example</a>
  <a href="#about">Example</a>
  <a class="icon" onclick="responsive()">&#9776;</a>
</div>
</nav>