javascript - 如何防止下拉菜单在用户单击时关闭？

Question

我关注了一个 tutorial在 W3Schools 网站上关于从按钮制作下拉菜单。一切正常，除了当用户在下拉菜单中单击时，菜单本身会消失。

我想制作一个登录按钮，用户点击该按钮，它会显示一个下拉菜单，他/她可以在其中输入他/她的用户名和密码，然后点击登录。

我想保留这个功能，如果用户点击下拉菜单外的任何其他区域，它会自动关闭下拉菜单。

我的问题是，当用户单击下拉菜单内部 的任何区域时，下拉菜单会消失。仅使用 JavaScript 在下拉菜单中单击时，如何防止它消失？使用 jQuery 怎么样(我还不太熟悉 jQuery)

/* 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');
      }
    }
  }
}

/* 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);
}

/* Contents inside the dropdown */
.dropdown-content input, .dropdown-content button {
    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;}

<div class="dropdown">
  <button onclick="myFunction()" class="dropbtn">LOG IN</button>
  <div id="myDropdown" class="dropdown-content">
    <input type="text" name="username" placeholder="Enter username"/>
    <input type="text" name="password" placeholder="Enter password"/>
    <button type="submit" name="submit">Submit</button>
  </div>
</div>

Answer 1

在 window.onClick 处理程序中，我们添加了一个条件来排除“下拉内容”及其子项。

/* 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')) {
    // [BEGIN][Here is the condition]
    if (event.target.matches('.dropdown-content') || event.target.matches('.dropdown-content *') ) {
       event.stopPropagation();
       return;
    }
  // [END][Here is the condition]
    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');
      }
    }
  }
}

/* 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);
}

/* Contents inside the dropdown */
.dropdown-content input, .dropdown-content button {
    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;}

<div class="dropdown">
  <button onclick="myFunction()" class="dropbtn">LOG IN</button>
  <div id="myDropdown" class="dropdown-content">
    <input type="text" name="username" placeholder="Enter username"/>
    <input type="text" name="password" placeholder="Enter password"/>
    <button type="submit" name="submit">Submit</button>
  </div>
</div>