动态更改子菜单的标题

Question

我想创建一个类别下拉菜单。当页面首次加载时，我希望下拉菜单显示“类别”。我希望能够点击像“Tops”这样的类别。然后下拉菜单的标题变为“Tops”而不是类别。不太确定如何开始，我对编码很陌生。在 W3 上找到了一些代码用作我的基线。

  <button onclick="myFunction()" class="dropbtn">Dropdown</button>
  <div id="myDropdown" class="dropdown-content">
    <a href="#">Link 1</a>
    <a href="#">Link 2</a>
    <a href="#">Link 3</a>
  </div>
</div>

Javascript

toggle between hiding and showing the dropdown content */
function myFunction() {
  document.getElementById("myDropdown").classList.toggle("show");
}

// Close the dropdown menu if the user clicks outside of it
window.onclick = function(event) {
  if (!event.target.matches('.dropbtn')) {
    var dropdowns = document.getElementsByClassName("dropdown-content");
    var i;
    for (i = 0; i < dropdowns.length; i++) {
      var openDropdown = dropdowns[i];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

Answer 1

这是一种无需使用 JavaScript 只需 html 和 CSS 即可创建下拉菜单并使用 JavaScript 处理名称更改事件的方法

需要注意的重要一点是，在使用

设置新名称时

title.innerHTML = name ;

它会破坏原始列表并覆盖它，因此在该语句之后我们必须用

重新添加列表

title.appendChild(list)

这是工作代码...

var title = document.getElementById('title');
var list = document.getElementById('list');

let c1 = document.getElementById('c1');
let c2 = document.getElementById('c2');
let c3 = document.getElementById('c3');

var namec1 = c1.innerHTML; 
var namec2 = c2.innerHTML; 
var namec3 = c3.innerHTML; 

//console.log(name)
c1.addEventListener("click", function(e){

renameTitle(namec1)
// Add more event stuff here

});


c2.addEventListener("click", function(e){
renameTitle(namec2)
// Add more event stuff here

});


c3.addEventListener("click", function(e){
renameTitle(namec3)
// Add more event stuff here

});

function renameTitle(name)
{
  var title = document.getElementById('title');
  title.innerHTML = name ;
  title.appendChild(list)
}

a {
  text-decoration: none;
}

nav {
    font-family: monospace;
}

ul {
  background: darkorange;
    list-style: none;
    margin: 0;
    padding-left: 0;
}

li {
    color: #fff;
  background: darkorange;
    display: block;
    float: left;
    padding: 1rem;
    position: relative;
    text-decoration: none;
  transition-duration: 0.5s;
}
  
li a {
  color: #fff;
}

li:hover,
li:focus-within {
    background: red;
    cursor: pointer;
}

li:focus-within a {
  outline: none;
}

ul li ul {
    background: orange;
    visibility: hidden;
  opacity: 0;
  min-width: 5rem;
    position: absolute;
  transition: all 0.5s ease;
  margin-top: 1rem;
    left: 0;
  display: none;
}

ul li:hover > ul,
ul li:focus-within > ul,
ul li ul:hover,
ul li ul:focus {
  visibility: visible;
  opacity: 1;
  display: block
}

ul li ul li {
    clear: both;
  width: 100%;
}

<nav role="navigation">
  <ul>
  <li id='title'> Categories
      <ul class="dropdown" id='list'>
        <li id='c1'>Sub-1</li>
        <li id='c2'>Sub-2</li>
        <li id='c3'>Sub-3</li>
      </ul>
    </li>
    

      
  </ul>
</nav>

一个和你的cmets的一部分创建一个categories元素并将它添加到列表中添加

var newItem = document.createElement('li');
newItem .innerHTML = 'catogories';

var list = document.getElementById("list");    // Get the <ul> element to insert a new node
list.insertBefore(newItem, list.childNodes[0]);  // Insert <li> before the first child of <ul>

    <nav role="navigation">
      <ul>
      <li id='title'> Categories
          <ul class="dropdown" id='list'>
            <li id='c1'>Sub-1</li>
            <li id='c2'>Sub-2</li>
            <li id='c3'>Sub-3</li>
          </ul>
        </li>
        

          
      </ul>
    </nav>