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)
});

为了加强Sudharshan的回答，我将其包装在一个媒体查询中，以防止在XS显示宽度上出现悬停……

@media (min-width:768px)
{
    ul.nav li.dropdown:hover > ul.dropdown-menu {
        display: block;    
    }

    .nav .dropdown-menu {
        margin-top: 0;
    }
}

标记中的插入符号也不是必需的，只是li的下拉类。

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

这招对我很管用:

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

为那些想在移动设备上使用默认功能的用户添加这个功能。可以设置min-width:…根据需要

@media only screen and (min-width: 1195px) {
  ul.nav li.dropdown:hover > ul.dropdown-menu {
    display: block;
  }
  ul.nav li.dropdown> ul.dropdown-menu {
    display: none;
  }
}

设置display: none，这样下拉开关就不会产生问题。如果保持原样，可能会同时打开两个下拉列表。

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;
}