这是一款基于Bootstrap和Bootsnav的多级导航菜单。该多级导航菜单通过简单的CSS代码来对菜单进行美化，制作鼠标滑过的动画效果。

使用方法

在页面中引入bootstrap相关文件和bootsnav相关文件。

<link href="css/bootstrap.min.css" rel="stylesheet">
<link rel="stylesheet" href="css/bootsnav.css"/>
<script src="path/to/jquery.min.js"></script>
<script type="text/javascript" src="js/bootstrap.min.js"></script>
<script type="text/javascript" src="js/bootsnav.js"></script>
HTML结构

该Bootstrap多级导航菜单的基本HTML结构如下：

<div class="container">
    <div class="row">
        <div class="col-md-12">
            <nav class="navbar navbar-default navbar-mobile bootsnav">
                <div class="navbar-header">
                    <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#navbar-menu">
                        <i class="fa fa-bars"></i>
                    </button>
                </div>
                <div class="collapse navbar-collapse" id="navbar-menu">
                    <ul class="nav navbar-nav" data-in="fadeInDown" data-out="fadeOutUp">
                        <li alt="HOME"><a href="#">Home</a></li>
                        <li alt="ABOUT US"><a href="#">About Us</a></li>
                        <li class="dropdown" alt="SHORTCODES">
                            <a href="#" class="dropdown-toggle" data-toggle="dropdown">Shortcodes</a>
                            <ul class="dropdown-menu">
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                                <li class="dropdown">
                                    <a href="#" class="dropdown-toggle" data-toggle="dropdown" >Sub Menu</a>
                                    <ul class="dropdown-menu">
                                        <li><a href="#">Custom Menu</a></li>
                                        <li><a href="#">Custom Menu</a></li>
                                        <li class="dropdown">
                                            <a href="#" class="dropdown-toggle" data-toggle="dropdown" >Sub Menu</a>
                                            <ul class="dropdown-menu multi-dropdown">
                                                <li><a href="#">Custom Menu</a></li>
                                                <li><a href="#">Custom Menu</a></li>
                                                <li><a href="#">Custom Menu</a></li>
                                                <li><a href="#">Custom Menu</a></li>
                                            </ul>
                                        </li>
                                        <li><a href="#">Custom Menu</a></li>
                                    </ul>
                                </li>
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                            </ul>
                        </li>
                        <li class="dropdown" alt="PAGES">
                            <a href="#" class="dropdown-toggle" data-toggle="dropdown">Pages</a>
                            <ul class="dropdown-menu">
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                                <li class="dropdown">
                                    <a href="#" class="dropdown-toggle" data-toggle="dropdown">Sub Menu</a>
                                    <ul class="dropdown-menu">
                                        <li><a href="#">Custom Menu</a></li>
                                        <li><a href="#">Custom Menu</a></li>
                                        <li class="dropdown">
                                            <a href="#" class="dropdown-toggle" data-toggle="dropdown">Sub Menu</a>
                                            <ul class="dropdown-menu multi-dropdown">
                                                <li><a href="#">Custom Menu</a></li>
                                                <li><a href="#">Custom Menu</a></li>
                                                <li><a href="#">Custom Menu</a></li>
                                                <li><a href="#">Custom Menu</a></li>
                                            </ul>
                                        </li>
                                        <li><a href="#">Custom Menu</a></li>
                                    </ul>
                                </li>
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                                <li><a href="#">Custom Menu</a></li>
                            </ul>
                        </li>
                        <li alt="PORTFOLIO"><a href="#">Portfolio</a></li>
                        <li alt="CONTACT US"><a href="#">Contact Us</a></li>
                    </ul>
                </div>
            </nav>
        </div>
    </div>
</div>
CSS样式

为该Bootstrap多级导航菜单添加以下的CSS样式：

nav.navbar.bootsnav{
    border: none;
    background: none;
    margin-bottom: 150px;
}
nav.navbar.bootsnav ul.nav > li{
    margin-right: 10px;
}
nav.navbar.bootsnav ul.nav > li:before{
    content: attr(alt);
    padding: 15px;
    font-size: 14px;
    font-weight: 600;
    color: #fff;
    opacity: 0;
    overflow: hidden;
    position: absolute;
    top: 0;
    left: 0;
    transform: scale(1.2);
    transition: all 0.3s ease 0s;
}
nav.navbar.bootsnav ul.nav > li:hover:before{
    transform: scale(1);
    opacity: 1;
}
nav.navbar.bootsnav ul.nav > li > a{
    padding: 15px;
    margin: 0;
    /*color: rgba(0, 0, 0, 0.4);*/
    color: #D5D6E2;
    text-transform: uppercase;
    z-index: 1;
    transition: all 0.5s ease 0s;
}
nav.navbar.bootsnav ul.nav > li.dropdown > a{
    padding: 15px 30px 15px 15px;
}
nav.navbar.bootsnav ul.nav > li > a:hover,
nav.navbar.bootsnav ul.nav > li.on > a{ color: #fff; }
nav.navbar.bootsnav ul.nav > li.dropdown > a.dropdown-toggle:after{
    position: absolute;
    margin: 0 0 0 7px;
}
nav.navbar.bootsnav ul.nav > li.dropdown > ul{
    top: 120%;
    transition: all 0.8s ease 0s;
}
nav.navbar.bootsnav ul.nav > li.dropdown.on > ul{
    top: 100%;
}
.dropdown-menu.multi-dropdown{
    position: absolute;
    left: -100% !important;
}
nav.navbar.bootsnav li.dropdown ul.dropdown-menu{
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
    border: none;
}
@media only screen and (max-width:990px){
    .dropdown-menu.multi-dropdown{ left: 0 !important; }
    nav.navbar.bootsnav .navbar-toggle{
        background: none;
        color: #fff;
    }
    nav.navbar.bootsnav ul.nav > li{
        margin-right: 0;
    }
    nav.navbar.bootsnav ul.nav > li:before{
        width: 100%;
        font-weight: normal;
        color: #555;
    }
    nav.navbar.bootsnav ul.nav > li > a{
        color: #333 !important;
        border-top: none;
    }
    nav.navbar.bootsnav ul.nav > li > a:hover{
        color: #333;
    }
    nav.navbar.bootsnav ul.nav > li.dropdown > ul{ top: 100%; }
}