一款基于jquery和css3的响应式二级导航菜单

  <div id="header">
        <div class="logo">
            <a href="#">Responsive Nav</a>
        </div>
        <nav>
            <form class="search" action="search.php">
            <input name="q" placeholder="Search..." type="search">
            </form>
            <ul>
                <li><a href="">Home</a> </li>
                <li><a href="">About</a>
                    <ul class="mega-dropdown">
                        <li class="row">
                            <ul class="mega-col">
                                <li><a href="#">About</a></li>
                                <li><a href="#">About</a></li>
                                <li><a href="#">Contact</a></li>
                                <li><a href="#">Contact</a></li>
                            </ul>
                            <ul class="mega-col">
                                <li><a href="#">Help</a></li>
                                <li><a href="#">Pricing</a></li>
                                <li><a href="#">Team</a></li>
                                <li><a href="#">Services</a></li>
                            </ul>
                            <ul class="mega-col">
                                <li><a href="#">Coming Soon</a></li>
                                <li><a href="#">404 Error</a></li>
                                <li><a href="#">Search</a></li>
                                <li><a href="#">Author Page</a></li>
                            </ul>
                            <ul class="mega-col">
                                <li><a href="#">Full Width</a></li>
                                <li><a href="#">Right Column</a></li>
                                <li><a href="#">Left Column</a></li>
                                <li><a href="#">Maintenance</a></li>
                            </ul>
                        </li>
                    </ul>
                </li>
                <li class="dropdown"><a href="">Contact</a>
                    <ul>
                        <li><a href="#">About Version</a></li>
                        <li><a href="#">About Version</a></li>
                        <li><a href="#">Contact Us</a></li>
                        <li><a href="#">Contact Us</a></li>
                    </ul>
                </li>
                <li><a href="">Portfolio</a> </li>
                <li><a href="">Team</a> </li>
            </ul>
        </nav>
    </div>

      *, *:before, *:after
        {
            -moz-box-sizing: border-box;
            -webkit-box-sizing: border-box;
            box-sizing: border-box;
            margin: 0;
            padding: 0;
        }
        body
        {
            background: #bdc3c7;
            line-height: 1.5;
            font-family: sans-serif;
            text-transform: uppercase;
            font-size: 16px;
            color: #fff;
        }
        a
        {
            text-decoration: none;
            color: #fff;
        }
        #header
        {
            background: #1E262D;
            width: 100%;
            position: relative;
        }
        #header:after
        {
            content: "";
            clear: both;
            display: block;
        }
        .search
        {
            float: right;
            padding: 30px;
        }
        input
        {
            border: none;
            padding: 10px;
            border-radius: 20px;
        }
        .logo
        {
            float: left;
            padding: 26px 0 26px;
        }
        .logo a
        {
            font-size: 28px;
            display: block;
            padding: 0 0 0 20px;
        }
        nav
        {
            float: right;
        }
        nav > ul
        {
            float: left;
            position: relative;
        }
        nav li
        {
            list-style: none;
            float: left;
        }
        nav .dropdown
        {
            position: relative;
        }
        nav li a
        {
            float: left;
            padding: 35px;
        }
        nav li a:hover
        {
            background: #2C3E50;
        }
        nav li ul
        {
            display: none;
        }
        nav li:hover ul
        {
            display: inline;
        }
        nav li li
        {
            float: none;
        }
        nav .dropdown ul
        {
            position: absolute;
            left: 0;
            top: 100%;
            background: #fff;
            padding: 20px 0;
            border-bottom: 3px solid #34495e;
        }
        nav .dropdown li
        {
            white-space: nowrap;
        }
        nav .dropdown li a
        {
            padding: 10px 35px;
            font-size: 13px;
            min-width: 200px;
        }
        nav .mega-dropdown
        {
            width: 100%;
            position: absolute;
            top: 100%;
            left: 0;
            background: #fff;
            overflow: hidden;
            padding: 20px 35px;
            border-bottom: 3px solid #34495e;
        }
        nav li li a
        {
            float: none;
            color: #333;
            display: block;
            padding: 8px 10px;
            border-radius: 3px;
            font-size: 13px;
        }
        nav li li a:hover
        {
            background: #bdc3c7;
            background: #FAFBFB;
        }
        .mega-col
        {
            width: 25%;
            float: left;
        }
        #menu-icon
        {
            position: absolute;
            right: 0;
            top: 50%;
            margin-top: -12px;
            margin-right: 30px;
            display: none;
        }
        #menu-icon span
        {
            border: 2px solid #fff;
            width: 30px;
            margin-bottom: 5px;
            display: block;
            -webkit-transition: all .2s;
            transition: all .1s;
        }
        @media only screen and (max-width: 1170px)
        {
            nav > ul > li > a
            {
                padding: 35px 15px;
            }
        }
        @media only screen and (min-width: 960px)
        {
            nav
            {
                display: block !important;
            }
        }
        @media only screen and (max-width: 959px)
        {
            nav
            {
                display: none;
                width: 100%;
                clear: both;
                float: none;
                max-height: 400px;
                overflow-y: scroll;
            }
            #menu-icon
            {
                display: inline;
                top: 45px;
                cursor: pointer;
            }
            #menu-icon.active .first
            {
                transform: rotate(45deg);
                -webkit-transform: rotate(45deg);
                margin-top: 10px;
            }
            #menu-icon.active .second
            {
                transform: rotate(135deg);
                -webkit-transform: rotate(135deg);
                position: relative;
                top: -9px;
            }
            #menu-icon.active .third
            {
                display: none;
            }
            .search
            {
                float: none;
            }
            .search input
            {
                width: 100%;
            }
            nav
            {
                padding: 10px;
            }
            nav ul
            {
                float: none;
            }
            nav li
            {
                float: none;
            }
            nav ul li a
            {
                float: none;
                padding: 8px;
                display: block;
            }
            #header nav ul ul
            {
                display: block;
                position: static;
                background: none;
                border: none;
                padding: 0;
            }
            #header nav a
            {
                color: #fff;
                padding: 8px;
            }
            #header nav a:hover
            {
                background: #fff;
                color: #333;
                border-radius: 3px;
            }
            #header nav ul li li a:before
            {
                content: "- ";
            }
            .mega-col
            {
                width: 100%;
            }
        }

  $(‘#header‘).prepend(‘<div id="menu-icon"><span class="first"></span><span class="second"></span><span class="third"></span></div>‘);
        $(‘#menu-icon‘).on(‘click‘, function () {
            window.CP.stopExecutionOnTimeout(1);
            $(‘nav‘).slideToggle();
            $(this).toggleClass(‘active‘);
        }); //@ sourceURL=pen.js