如何在打开另一个 Javascript 下拉菜单时关闭另一个

Question

我对 JavaScript 不熟悉，我希望能在我似乎无法解决的问题上获得一些帮助。我的网站上目前有 2 个下拉菜单。一个是导航的下拉菜单，单击汉堡菜单图标时会激活该菜单。第二个下拉菜单用于在我的网站上显示类别。目前，当我单击一个下拉菜单时，我必须再次单击它才能关闭它。如果我单击第二个下拉菜单而不关闭第一个下拉菜单，则两者都将保持可见。我想要发生的是两件事。首先，我希望这样，如果用户单击 div 之外的任何位置以获取下拉菜单，它会自动关闭。我希望看到的第二件事是一次只能看到一个下拉菜单。因此，如果我单击一个并且另一个下拉菜单打开，我希望它关闭。希望我解释得很好。现在进入我正在使用的代码。

以下内容在我脑海中。

<script>
/* When the user clicks on the button,
toggle between hiding and showing the dropdown content */
function DropDownMenuNavigation() {
document.getElementById("b2DropDownMenuNav").classList.toggle("show");
}
function DropDownMenuCategory() {
document.getElementById("b2DropDownMenuCat").classList.toggle("show");  
}
</script>

然后我使用它作为按钮来激活导航下拉菜单。这包含在我的身体里。

<div class="dropbtn" style="float: left;">
<button onclick="DropDownMenuNavigation()" class="dropbtn">&#9776; MENU</button>
</div>

这是我用来包含我的类别下拉菜单的东西。

<div class="dropbtn" style="float: left;">
<button onclick="DropDownMenuCategory()" class="dropbtn">CATEGORIES</button>
</div>

现在最后是我使用的 css，只是偶然有帮助。

/* Dropdown Button */
.dropbtn {
background-color: #0066a2;
color: white;
padding: 1px;
font-size: 15px;
font-weight: bold;
border: none;
cursor: pointer;
}
.dropbtn a {
color: #FFFFFF;
text-decoration: none;
font-size: 15px;
font-weight: bold;
}

/* The container <div> - needed to position the dropdown content */
.dropdown {
float: left;
position: relative;
display: inline-block;
}

/* Dropdown Content (Hidden by Default) */
.dropdown-content {
display: none;
position: absolute;
background-color: #0066a2;
min-width: 260px;
max-width: 960px;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
z-index: 1;
}

/* Links inside the dropdown  */
.dropdown-content a {
color: #000000;
text-decoration: none;
}

/* 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;} 

那么，按照我的要求，最好的方法是什么？有人可以帮我一把，并指出我正确的方向。非常感谢，感谢您提供给我的任何帮助。

Answer 1

onclick 属性不应包含()。它应该是这样的：

<button onclick="DropDownMenuNavigation" class="dropbtn">&#9776; MENU</button>

或者——甚至更好——不要将事件侦听器内联，而是将其放入脚本中。

此外，当按下按钮时，从另一个下拉列表中删除“显示”类。

看这里：

document.getElementById('menudropbtn').addEventListener('click', function () {
	document.getElementById('b2DropDownMenuNav').classList.toggle('show')
  document.getElementById('b2DropDownMenuCat').classList.remove('show')
})

document.getElementById('categoriesdropbtn').addEventListener('click', function () {
	document.getElementById('b2DropDownMenuCat').classList.toggle('show')
  document.getElementById('b2DropDownMenuNav').classList.remove('show')
})

/* Dropdown Button */
.dropbtn {
  background-color: #0066a2;
  color: white;
  padding: 1px;
  font-size: 15px;
  font-weight: bold;
  border: none;
  cursor: pointer;
}

.dropbtn a {
  color: #FFFFFF;
  text-decoration: none;
  font-size: 15px;
  font-weight: bold;
}


/* The container <div> - needed to position the dropdown content */
.dropdown {
  float: left;
  position: relative;
  display: inline-block;
}


/* Dropdown Content (Hidden by Default) */
.dropdown-content {
  display: none;
  position: absolute;
  background-color: #0066a2;
  min-width: 260px;
  max-width: 960px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
}


/* Links inside the dropdown  */
.dropdown-content a {
  color: #000000;
  text-decoration: none;
}


/* 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="dropbtn" style="float: left;">
  <button class="dropbtn" id="menudropbtn">&#9776; MENU</button>
  <div class="dropdown">
    <div class="dropdown-content" id="b2DropDownMenuNav">
      <a>Something</a>
    </div>
  </div>
</div>

<div class="dropbtn" style="float: left;">
  <button class="dropbtn" id="categoriesdropbtn">CATEGORIES</button>
  <div class="dropdown">
    <div class="dropdown-content" id="b2DropDownMenuCat">
      <a>Something else</a>
    </div>
  </div>
</div>

Answer 2

为此，您可以添加自定义 JS 函数，这些函数将根据元素 ID 打开下拉菜单，并且当打开一个下拉菜单时，将关闭所有其他下拉菜单。您可以创建一个关闭所有下拉列表的函数。然后，在你的“open”函数中，首先调用“close_all”函数。

这是一个有效的 sn-p。

// Functions for Interactive File Menu Bar 
// - Click Butoon to Open Dropdown
// - Clicking one dropdown closes all other
// - Clicking outside the file menu bar will close all the dropdown.

function open_dropdown(element_id) {
  console.log('Opening Dropdown:', element_id)
  close_all_dropdowns()
  document.getElementById(element_id).style.display = 'block';
}

// Close the dropdown if the user clicks outside of it
function close_dropdown(element) {
  console.log('I am closing dropdown:', element)
  element.style.display = 'none'
}

// Close all dropdowns.
function close_all_dropdowns() {
  var dropdowns = document.getElementsByClassName('dropdown-content')
  for (var i = 0; i < dropdowns.length; i++) {
    close_dropdown(dropdowns[i]);
  }
}

// Close all dropdowns when clicking outside.
window.onclick = function (e) {
  if (!e.target.matches('.dropbtn')) {
    close_all_dropdowns()
  }
}

/* Styles for the File Menu Bar. */
.dropdown {
  position: relative;
  display: inline-block;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f1f1f1;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
}


.dropdown-content a {
  float: none;
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
  text-align: left;
}

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <link rel="stylesheet" href="https://unpkg.com/98.css">
  <link rel="stylesheet" href="style.css">
  <script src="script.js"></script>
  <title>RetroNet</title>
</head>

<body>

  <div class="window" style="width: 100%">
    <div class="title-bar">
      <div class="title-bar-text">Welcome to RetroNet!</div>
      <div class="title-bar-controls">
        <button aria-label="Minimize"></button>
        <button aria-label="Maximize"></button>
        <button aria-label="Close"></button>
      </div>
    </div>

    <!-- Main menu -->
    <div class="window-body">
      <div class="dropdown">
        <button class="dropbtn" onclick="open_dropdown('dd_file')">File</button>
        <div class="dropdown-content" id="dd_file">
          <a href="#">Open</a>
          <a href="#">Close</a>
          <a href="#">Settings</a>
        </div>
      </div>
      <div class="dropdown">
        <button class="dropbtn" onclick="open_dropdown('dd_edit')">Edit</button>
        <div class="dropdown-content" id="dd_edit">
          <a href="#">Cut</a>
          <a href="#">Copy</a>
          <a href="#">Paste</a>
        </div>
      </div>
      <div class="dropdown">
        <button class="dropbtn" onclick="open_dropdown('dd_view')">View</button>
        <div class="dropdown-content" id="dd_view">
          <a href="#">Toggle CSS</a>
          <a href="#">Toggle Javascript</a>
        </div>
      </div>
      <div class="dropdown">
        <button class="dropbtn" onclick="open_dropdown('dd_tools')">Tools</button>
        <div class="dropdown-content" id="dd_tools">
          <a href="#">Not Decided</a>
        </div>
      </div>
      <div class="dropdown">
        <button class="dropbtn" onclick="open_dropdown('dd_favorite')">Favourties</button>
        <div class="dropdown-content" id="dd_favorite">
          <a href="#">Add New Favorite</a>
          <a href="#">Add this Page to Favorites</a>
          <a href="#">Show Favorites</a>
        </div>
      </div>
      <div class="dropdown">
        <button class="dropbtn" onclick="open_dropdown('dd_help')">Help</button>
        <div class="dropdown-content" id="dd_help">
          <a
            href="https://github.com/ayushxx7/summer-code-jam-2020/blob/master/adventurous-anteaters/README.md">README</a>
        </div>
      </div>
    </div>
  </div>

</body>

</html>

Answer 3

也许以下代码可以提供帮助。您可以使用自定义事件让模块项（如菜单、弹出窗口等）相互通信。

如果单击菜单按钮，则可以调度自定义事件。页面上的任何其他项目都可以根据此事件执行某些操作（例如在打开主菜单时暂停游戏）。

// find menu-content in item (=menu-button) and return
//  "none" if menu-content.style.display is "block"
//  "block" if menu-content.style.display is not "block"
const toggle =
  (item) => {
    const content = 
      item.querySelector("[x-role=\"menu-content\"]");
    return content.style.display === "block"
      ? "none"
      : "block"
  }
;
// set menu-content found in item (=menu-button) to
//  none or block
const changeDisplay =
  (item,display) =>
    item.querySelector("[x-role=\"menu-content\"]")
      .style.display = display;
// when menu-button is clicked
const menuButtonClicked = 
  e => {
    //get the toggled content style
    //  if current style is block then
    //  toggled is none and vice versa
    const style = toggle(e.target);
    //hide all menus, in the for each we
    //  added an event listener for "menu-click" event
    //  the listener will hide the menu
    var evt = new Event("menu-click",{});
    document.body.dispatchEvent(evt);
    //set style of the current
    changeDisplay(e.target,style);
  }
;
//for each menu-botton role 
//  I am not using css selectors on class, class is for style, 
//  user defined properties can be used for behavior. 
//  If you mix this up then you can break style, behavior
//  or both when changing behavior or style
document.querySelectorAll("[x-role=\"menu-button\"]")
  .forEach(
    x => {
      //when clicked let menuButtonClicked handle it
      x.addEventListener(
        "click"
        ,menuButtonClicked
      );
      //listen to custom event called "menu-click"
      //  set display to none when this happens
      //  if you were to dynamically add and remove
      //  menu items then you should remove the event
      //  listeners when you remove the menu
      document.body.addEventListener(
        "menu-click"
        ,e => changeDisplay(x,"none")        
      );
    }
  )
;

.menu-button {
  cursor: pointer;
}
.menu-content {
  display:none;
}

<div class="menu-button" x-role="menu-button">
 menu1
 <div class="menu-content" x-role="menu-content">
  <ul>
    <li>one</li>
    <li>two</li>
  </ul>
 </div>
</div>
<div class="menu-button" x-role="menu-button">
 menu2
 <div class="menu-content" x-role="menu-content">
  <ul>
    <li>three</li>
    <li>four</li>
  </ul>
 </div>
</div>
<div class="menu-button" x-role="menu-button">
 menu3
 <div class="menu-content" x-role="menu-content">
  <ul>
    <li>five</li>
    <li>six</li>
  </ul>
 </div>
</div>