我们看到，除了“My Head Hurts”的答案，“Cory Price”还发现了两个问题:

问题1:单击下拉链接将打开下拉菜单。它会一直打开，除非用户点击某个地方 或者返回到它上面，创建一个尴尬的UI。 解决方案:从导航链接中删除“class”和“data-toggle”元素

这个解决方案近乎完美，但这里的问题是，当涉及到移动设备和平板电脑时，它就行不通了!

我使用了一些jQuery代码来修复这个问题..

if ($(window).width() > 769) {
    $('.dropdown-toggle').removeAttr('data-toggle');
    $('.dropdown-menu').removeAttr('style');
    $('.dropdown').removeClass('open');
}
$(window).resize(function () {
    if ($(window).width() > 769) {
        $('.dropdown-toggle').removeAttr('data-toggle');
        $('.dropdown-menu').removeAttr('style');
        $('.dropdown').removeClass('open');
    }
    else {
        $('.dropdown-toggle').attr("data-toggle", "dropdown");
    }
});

注意:这里我们假设移动设备和平板电脑的折痕从768px开始。

这样就把上面的隐藏起来了

.navbar .dropdown-menu:before {
   display:none;
}
.navbar .dropdown-menu:after {
   display:none;
}

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
  }
}

这是Bootstrap 3内置的。 只需将此添加到您的CSS:

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

我是这样做的:

$('ul.nav li.dropdown').hover(function(){
       $(this).children('ul.dropdown-menu').slideDown(); 
    }, function(){
       $(this).children('ul.dropdown-menu').slideUp(); 
});

我希望这能帮助到一些人……

以下是我的技巧，它在你停止在菜单或切换按钮上悬停后，在菜单关闭之前添加了轻微的延迟。你通常点击来显示导航菜单的<按钮>是#nav_dropdown。

$(function() {
  var delay_close_it, nav_menu_timeout, open_it;
  nav_menu_timeout = void 0;
  open_it = function() {
    if (nav_menu_timeout) {
      clearTimeout(nav_menu_timeout);
      nav_menu_timeout = null;
    }
    return $('.navbar .dropdown').addClass('open');
  };
  delay_close_it = function() {
    var close_it;
    close_it = function() {
      return $('.navbar .dropdown').removeClass('open');
    };
    return nav_menu_timeout = setTimeout(close_it, 500);
  };
  $('body').on('mouseover', '#nav_dropdown, #nav_dropdown *', open_it).on('mouseout', '#nav_dropdown', delay_close_it);
  return $('body').on('mouseover', '.navbar .dropdown .dropdown-menu', open_it).on('mouseout', '.navbar .dropdown .dropdown-menu', delay_close_it);
});