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
  }
}

最标准的回答:

支持aria-expanded属性 支持非触摸设备 支持触摸设备 支持所有下拉菜单

var isTouchDevice = (('ontouchstart' in window) ||
                                (navigator.MaxTouchPoints > 0) ||
                                (navigator.msMaxTouchPoints > 0));
if(!isTouchDevice){
    // open dropdowns on hover on non mobile devices
    $(".dropdown").hover(function(e) {
        $('.dropdown-toggle', this).dropdown("toggle");
        e.stopPropagation();
    });
    // prevent blinkling
    $(".submenu-link").click(function(e) {
        e.stopPropagation();
    });
}

如果你需要，你可以将$(".dropdown")更改为特定的区域:

$("#top-menu .dropdown")

对于插入符号…我还没见过有人指定简单的CSS完全阻止插入符号。

给你:

.caret {
    display: none !important;
}

这个也可以。

$('.dropdown').on('mouseover',function(){
    $(this).find('.dropdown-menu').show();
});
$('.dropdown').on('mouseleave',function(){
    $(this).find('.dropdown-menu').hide();
});

如果下拉菜单在悬停元素之间有间隙，下拉菜单将立即关闭，如图所示

为了防止这种行为，您可以为事件添加一个100毫秒的超时

let dropdownTimer;
$('.dropdown').on('mouseover', () => {
    clearTimeout(dropdownTimer)
    $(this).find('.dropdown-menu').show();
});
$('.dropdown').on('mouseleave', () =>{
    dropdownTimer = setTimeout(() => {
        $(this).find('.dropdown-menu').hide();
    }, 100)
});

Bootstrap 4, 2019

我读了很多这样的答案，但最后我自己做了，因为这不是我需要的。

我有引导4，并希望保持点击+悬停功能。此外，我想启用它只有下拉有一个额外的类“.open-on-hover”。

我还想保持Bootstrap的Jquery定位下拉菜单时，它是旁边的页面边缘。所以我们不仅仅要做"display: block"我们想要完整的Bootstrap工作方式。所以我只是触发点击。

逻辑是，如果它是mouseenter则打开它，如果它是mouseleave则隐藏它，如果它是打开的

/**
 * Open Bootstrap 4 dropdown on hover
 */
$(document).on('mouseenter mouseleave', '.dropdown.open-on-hover', function(e) 
{
    let toggler = $(this).find('[data-toggle="dropdown"]').first();

    if(e.type === 'mouseenter') {
        $(toggler).trigger('click', 'open');
    } else if ($(this).children('.dropdown-menu.show').length) {
        $(toggler).trigger('click', 'close');
    }
});

html

<div class="dropdown open-on-hover">
    <div class="btn" data-toggle="dropdown">
        Hover or click me
    </div>
    <div class="dropdown-menu">
        <a class="dropdown-item">
            Item 1
        </a>
        <a class="dropdown-item">
            Item 2
        </a>
    </div>
</div>

如果你有这样一个下拉类的元素(例如):

<ul class="list-unstyled list-inline">
    <li class="dropdown">
        <a data-toggle="dropdown" href="#"><i class="fa fa-bars"></i> Dropdown 1</a>
        <ul class="dropdown-menu">
            <li><a href="">Item 1</a></li>
            <li><a href="">Item 2</a></li>
            <li><a href="">Item 3</a></li>
            <li><a href="">Item 4</a></li>
            <li><a href="">Item 5</a></li>
        </ul>
    </li>
    <li class="dropdown">
        <a data-toggle="dropdown" href="#"><i class="fa fa-user"></i> Dropdown 2</a>
        <ul class="dropdown-menu">
            <li><a href="">Item A</a></li>
            <li><a href="">Item B</a></li>
            <li><a href="">Item C</a></li>
            <li><a href="">Item D</a></li>
            <li><a href="">Item E</a></li>
        </ul>
    </li>
</ul>

然后你可以让下拉菜单自动下拉悬停，而不是必须点击它的标题，通过使用这段jQuery代码:

<script>
    $('.dropdown').hover(
        function() {
            $(this).find('.dropdown-menu').stop(true, true).delay(200).fadeIn();
        },
        function() {
            $(this).find('.dropdown-menu').stop(true, true).delay(200).fadeOut();
        }
    );

    $('.dropdown-menu').hover(
        function() {
            $(this).stop(true, true);
        },
        function() {
            $(this).stop(true, true).delay(200).fadeOut();
        }
    );
</script>

这是一个演示

这个答案依赖于@Michael的答案，我做了一些改变，并添加了一些补充，以使下拉菜单正常工作