我希望这能有所帮助。查看链接https://jsfiddle.net/awb7gfb1/

<nav>
    <div id="menubar" class=" collapse navbar-collapse row">
        <ul id="dropdownNavbar" class="nav navbar-nav">
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn"><span class="glyphicon glyphicon-time"></span>
                Time Card
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a id="showTimeCard" href="#">My Time Card</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                    <a href="#">Sub Menu 4</a>
                    <a href="#">Sub Menu 5</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn"><span class="glyphicon glyphicon-stats"></span>
                Project
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn"><span class="glyphicon glyphicon-user"></span>
                HR Links
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn">
                <span class="glyphicon glyphicon-screenshot"></span>
                Leave Tracker
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                    <a href="#">Sub Menu 4</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn">
                <span class="glyphicon glyphicon-briefcase"></span>
                Accounts
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                    <a href="#">Sub Menu 4</a>
                    <a href="#">Sub Menu 5</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn">
                <span class="glyphicon glyphicon-headphones"></span>
                Service Desk
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                    <a href="#">Sub Menu 4</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn">
                <span class="glyphicon glyphicon-file"></span>
                Reports
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                    <a href="#">Sub Menu 4</a>
                    <a href="#">Sub Menu 5</a>
                </div>
            </li>
            <li class="dropdown">
                <button type="button" class="btn btn-primary dropbtn">
                <span class="glyphicon glyphicon-cog"></span>
                Settings
                <span class="caret"></span></button>
                <div class="dropdown-content">
                    <a href="#">Sub Menu 1</a>
                    <a href="#">Sub Menu 2</a>
                    <a href="#">Sub Menu 3</a>
                </div>
            </li>
        </ul>
    </div>
</nav>

还有CSS

.dropdown {
    float: left;
    padding-right: 1px;
}

.dropbtn{
    border: 0px;
    height: 30px;
    border-radius: 0px 10px;
}
li button, .dropbtn {
    display: inline-block;
    color: white;
    text-align: center;
}

li button:hover, .dropdown:hover .dropbtn {
    background-color: #12A5F4;
}

.dropbtn.active {
    background: #12A5F4;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #e8f3f4;
    min-width: 100%;
    box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.1);
    z-index: 10;
}

.navbar-header{
    overflow: visible;
    z-index: 1;
}

.dropdown-content a {
    color: black;
    padding: 5px 10px;
    display: block;
    text-align: left;
}

.dropdown-content a:hover {
    background-color: #d8dee2
}

.dropdown:hover .dropdown-content {
    display: block;
}

#menubar{
    padding-top: 5px;
    overflow: visible;
    z-index: 10;
    padding-left: 0px;
    padding-right: 0px;
    margin: 0px;
}

#dropdownNavbar{
    margin: 0px;
}

.navbar-toggle{
    background-color: #3382d5;
}
.navbar-toggle span{
    background-color: white;
}

只是想补充一下，如果你有多个下拉列表(就像我一样)，你应该这样写:

ul.nav li.dropdown:hover > ul.dropdown-menu {
    display: block;    
}

它会正常工作的。

最好的方法是用鼠标悬停来触发Bootstrap的点击事件。这样，它应该仍然保持触摸设备友好。

$('.dropdown').hover(function(){ 
  $('.dropdown-toggle', this).trigger('click'); 
});

引导版本4和5解决方案。(兼容)

这些都是使用mouseover和mouseleave事件和一些屏幕宽度检查的完整解决方案。这比纯CSS解决方案更好。

Bootstrap v5 -纯JS(用于webpack)

export class BootstrapOpenMenuHover {

/**
 * Constructor.
 */
constructor() {
  this.windowWidth = window.innerWidth;
  this.mobileBreakPoint = 991; // Put your menu break point here, when it switches to a hamburger icon.
  this.dropdownNavItems = document.querySelectorAll(".dropdown-toggle.nav-link");
  this.dropdownMenuItems = document.querySelectorAll(".dropdown-menu");

  this.setEventListeners();
}

/**
 * Set all of our event listeners.
 */
setEventListeners() {
  const _self = this;

  // To be safe set the width once the dom is loaded.
  window.addEventListener('load',  function () {
    _self.windowWidth = window.innerWidth;
  });

  // Keep track of the width in the event of a resize.
  window.addEventListener('resize',  function () {
    _self.windowWidth = window.innerWidth;
  });

  // Bind our hover events.
  if (_self.dropdownNavItems !== null)  {
    for (let i = 0; i < _self.dropdownNavItems.length; i++) {

      // On mouse enter.
      _self.dropdownNavItems[i].addEventListener('mouseenter', function () {
        if (_self.windowWidth >= _self.mobileBreakPoint) {
          this.classList.add('show');
          this.ariaExpanded = true;
          this.dataset.bsToggle = null;

          // Update the .dropdown-menu
          this.nextElementSibling.classList.add('show');
          this.nextElementSibling.dataset.bsPopper = 'none';
        }
      });

      // On mouse leave.
      _self.dropdownNavItems[i].addEventListener('mouseleave', function () {
        if (_self.windowWidth >= _self.mobileBreakPoint) {
          this.classList.remove('show');
          this.ariaExpanded = false;
          this.dataset.bsToggle = 'dropdown';

          // Update the .dropdown-menu
          this.nextElementSibling.classList.remove('show');
          this.nextElementSibling.dataset.bsPopper = null;
        }
      });
    }
  }

  // Bind events to .dropdown-menu items.
  if (_self.dropdownMenuItems !== null) {
    for (let i = 0; i < _self.dropdownMenuItems.length; i++) {
      // On mouse enter.
      _self.dropdownMenuItems[i].addEventListener('mouseenter', function () {
        if (_self.windowWidth >= _self.mobileBreakPoint) {
          this.classList.add('show');
          this.dataset.bsPopper = 'none';

          // Update the .dropdown-toggle
          this.previousElementSibling.classList.add('show');
          this.previousElementSibling.ariaExpanded = true;
          this.previousElementSibling.dataset.bsToggle = null;
        }
      });

      // On mouse leave.
      _self.dropdownMenuItems[i].addEventListener('mouseleave', function () {
        if (_self.windowWidth >= _self.mobileBreakPoint) {
          this.classList.remove('show');
          this.dataset.bsPopper = null;

          // Update the .dropdown-toggle
          this.previousElementSibling.classList.remove('show');
          this.previousElementSibling.ariaExpanded = false;
          this.previousElementSibling.dataset.bsToggle = 'dropdown';
        }
      });
    }
   }
  }
 }

 const bootstrapOpenMenuHover = new BootstrapOpenMenuHover();

Bootstrap v4方案

这将允许您遵循顶级导航链接。

这是基于桌面和移动平台设计的。随意更改BREAK_POINT变量以满足您的需要:D。

jQuery

var WINDOW_WIDTH;
var BREAK_POINT = 991;

(function ($) {

    /** Set window width onload */
    WINDOW_WIDTH = $(window).width(); // Returns width of browser viewport
    /** Set window width if the browser is resized */
    $(window).resize(function () {
        WINDOW_WIDTH = $(window).width(); // Returns width of browser viewport
    });

    /** Dropdown menu on mouseenter */
    $(".nav-item.dropdown").on('mouseenter', function () {
        console.log("mouseenter");
        if (WINDOW_WIDTH >= BREAK_POINT) {
            // Open up the dropdown
            $(this).addClass('show'); // add the class show to the li parent
            $(this).children('.nav-link').removeAttr('data-toggle'); // remove the data-toggle attribute so we can click and follow link
            $(this).children('.dropdown-menu').addClass('show'); // add the class show to the dropdown div sibling
        }
    });
    /** Dropdown menu on mouseleave */
    $(".nav-item.dropdown").on('mouseleave', function () {
        console.log("mouseleave");
        if (WINDOW_WIDTH >= BREAK_POINT) {
            // Close the dropdown
            $(this).removeClass('show'); // add the class show to the li parent
            $(this).children('.nav-link').attr('data-toggle', 'dropdown'); // remove the data-toggle attribute so we can click and follow link
            $(this).children('.dropdown-menu').removeClass('show'); // add the class show to the dropdown div sibling
        }
    });
});

CSS

@media(min-width:  768px) {
  .dropdown-menu {
    margin-top: 0; // fixes closing on slow mouse transition
  }
}

使用以下代码在鼠标悬停时打开子菜单(仅适用于桌面):

$('ul.nav li.dropdown').hover(function () {
    if ($(window).width() > 767) {
        $(this).find('.dropdown-menu').show();
    }
}, function () {
    if ($(window).width() > 767) {
        $(this).find('.dropdown-menu').hide().css('display','');
    }
});

如果你想让第一关菜单是可点击的，甚至在手机上也可以添加这个:

    $('.dropdown-toggle').click(function() {
    if ($(this).next('.dropdown-menu').is(':visible')) {
        window.location = $(this).attr('href');
    }
});

子菜单(下拉菜单)将打开鼠标悬停在桌面上，点击/触摸移动和平板电脑。 一旦子菜单打开，第二次单击将让您打开链接。 多亏了if ($(window).width() > 767)，子菜单将在移动设备上采用全屏宽度。

这招对我很管用:

.dropdown:hover .dropdown-menu {
    display: block;
}