javascript - 如何通过单击页面上的任意位置来关闭下拉菜单？

Question

下面是 w3schools 提供的 javascript 下拉菜单的简单代码，我想要两个下拉菜单，所以我创建了一个具有更改的元素和变量名称的副本。两个下拉菜单都可以正常工作，除了现在我无法通过单击网页上的任意位置来关闭打开的下拉菜单，而一个下拉菜单可以正常工作。那么我怎样才能在有两个下拉菜单的同时完成这项工作。

/* When the user clicks on the button,
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');
      }
    }
  }
}


/* When the user clicks on the button,
toggle between hiding and showing the dropdown content */
function myFunction2() {
  document.getElementById("myDropdown2").classList.toggle("show");
}

// Close the dropdown menu if the user clicks outside of it
window.onclick = function(event) {
  if (!event.target.matches('.dropbtn2')) {

    var dropdown = document.getElementsByClassName("dropdown-content2");
    var e;
    for (e = 0; i < dropdown.length; e++) {
      var opendropdown = dropdown[e];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

/* Dropdown Button */

.dropbtn {
  background-color: #4CAF50;
  color: white;
  padding: 16px;
  font-size: 16px;
  border: none;
  cursor: pointer;
}
/* Dropdown button on hover & focus */

.dropbtn:hover,
.dropbtn:focus {
  background-color: #3e8e41;
}
/* The container <div> - needed to position the dropdown content */

.dropdown {
  position: relative;
  display: inline-block;
}
/* Dropdown Content (Hidden by Default) */

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
}
/* Links inside the dropdown */

.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}
/* Change color of dropdown links on hover */

.dropdown-content a:hover {
  background-color: #f1f1f1
}
/* Show the dropdown menu (use JS to add this class to the .dropdown-content container when the user clicks on the dropdown button) */

.show {
  display: block;
}
/* Dropdown Button */

.dropbtn2 {
  background-color: #4CAF50;
  color: white;
  padding: 16px;
  font-size: 16px;
  border: none;
  cursor: pointer;
}
/* Dropdown button on hover & focus */

.dropbtn2:hover,
.dropbtn2:focus {
  background-color: #3e8e41;
}
/* The container <div> - needed to position the dropdown content */

.dropdown2 {
  position: relative;
  display: inline-block;
}
/* Dropdown Content (Hidden by Default) */

.dropdown-content2 {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
}
/* Links inside the dropdown */

.dropdown-content2 a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}
/* Change color of dropdown links on hover */

.dropdown-content2 a:hover {
  background-color: #f1f1f1
}
/* Show the dropdown menu (use JS to add this class to the .dropdown-content container when the user clicks on the dropdown button) */

.show {
  display: block;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<table>
  <tr>
    <td>
      <div class="dropdown">
        <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>
    </td>
    <td>
      <div class="dropdown2">
        <button onclick="myFunction2()" class="dropbtn">Dropdown2</button>
        <div id="myDropdown2" class="dropdown-content2">
          <a href="#">Link 1</a>
          <a href="#">Link 2</a>
          <a href="#">Link 3</a>
        </div>
      </div>
    </td>
  </tr>
</table>

Answer 1

您可以按照以下方式进行操作。切换类时无需编写该代码来删除类。

只需在窗口点击时删除。

/* When the user clicks on the button,
toggle between hiding and showing the dropdown content */
function myFunction(event) {
  event.stopPropagation();
  document.getElementById("myDropdown").classList.toggle("show");
}

function myFunction2(event) {
  event.stopPropagation();
  document.getElementById("myDropdown2").classList.toggle("show");
}

// Close the dropdown menu if the user clicks outside of it
window.onclick = function(event) {
  document.getElementById("myDropdown").classList.remove("show");
  document.getElementById("myDropdown2").classList.remove("show");
}

/* Dropdown Button */

.dropbtn {
  background-color: #4CAF50;
  color: white;
  padding: 16px;
  font-size: 16px;
  border: none;
  cursor: pointer;
}
/* Dropdown button on hover & focus */

.dropbtn:hover,
.dropbtn:focus {
  background-color: #3e8e41;
}
/* The container <div> - needed to position the dropdown content */

.dropdown {
  position: relative;
  display: inline-block;
}
/* Dropdown Content (Hidden by Default) */

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
}
/* Links inside the dropdown */

.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}
/* Change color of dropdown links on hover */

.dropdown-content a:hover {
  background-color: #f1f1f1
}
/* Show the dropdown menu (use JS to add this class to the .dropdown-content container when the user clicks on the dropdown button) */

.show {
  display: block;
}
/* Dropdown Button */

.dropbtn2 {
  background-color: #4CAF50;
  color: white;
  padding: 16px;
  font-size: 16px;
  border: none;
  cursor: pointer;
}
/* Dropdown button on hover & focus */

.dropbtn2:hover,
.dropbtn2:focus {
  background-color: #3e8e41;
}
/* The container <div> - needed to position the dropdown content */

.dropdown2 {
  position: relative;
  display: inline-block;
}
/* Dropdown Content (Hidden by Default) */

.dropdown-content2 {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
}
/* Links inside the dropdown */

.dropdown-content2 a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}
/* Change color of dropdown links on hover */

.dropdown-content2 a:hover {
  background-color: #f1f1f1
}
/* Show the dropdown menu (use JS to add this class to the .dropdown-content container when the user clicks on the dropdown button) */

.show {
  display: block;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<table>
  <tr>
    <td>
      <div class="dropdown">
        <button onclick="myFunction(event)" 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>
    </td>
    <td>
      <div class="dropdown2">
        <button onclick="myFunction2(event)" class="dropbtn">Dropdown2</button>
        <div id="myDropdown2" class="dropdown-content2">
          <a href="#">Link 1</a>
          <a href="#">Link 2</a>
          <a href="#">Link 3</a>
        </div>
      </div>
    </td>
  </tr>
</table>