SOURCE

    $('.menu-w').on('click', function() {
        $(this).toggleClass('on');
    });

    <div style="max-width:750px;margin:0 auto;">
        <header class="header">
            <a class="back-btn" href="javascript:history.back()"><i class="iconfont icon-back"></i></a>
            <h1 class="h1vt">标题</h1>
            <div class="menu-w">
                <div class="top-icon-w">
                    <i class="icon-menu"></i>
                </div>
            </div>
            
            <div class="sub-nav-w">
                <ul class="sub-nav">
                    <li><a href="javascript:;"><i class="iconfont icon-home"></i>首页</a></li>
                    <li>
                        <a href="javascript:;"><i class="iconfont icon-ju"></i>开业聚惠</a>
                    </li>
                    <li>
                        <a href="javascript:;"><i class="iconfont icon-gou"></i>全球购</a>
                    </li>
                    <li>
                        <a href="javascript:;"><i class="iconfont icon-wuyi"></i>五一放价</a>
                    </li>
                </ul>
            </div>
        </header>
    </div>

body {
    font: 16px Microsoft YaHei, sans-serif;
    color: #2a2b2c;
    background: #fff;
}
a {
    text-decoration: none;
    display: block;
    color: #2a2b2c;
}





.header {
    height: 50px;
    position: relative;
    background: #0cd;
}
.iconfont {
    color: #555;
    font-size: 24px;
    vertical-align: -3px;
    margin-right: 10px;
}
.back-btn {
    width: 50px;
    height: 50px;
    position: absolute;
    top: 0;
    left: 0;
    text-align: center;
}
.back-btn .iconfont {
    color: #fff;
    font: 30px/50px arial;
}
.h1vt {
    font-size: 24px;
    font-weight: normal;
    line-height: 52px;
    text-align: center;
    padding: 0 60px 0 50px;
    color: #fff;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.menu-w {
    width: 60px;
    height: 50px;
    position: absolute;
    top: 0;
    right: 0;
    z-index: 5;
}
.top-icon-w {
    width: 26px;
    height: 19px;
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    margin: auto;
}
.top-icon-w .icon-menu {
    display: block;
    font-style: normal;
    width: 100%;
    height: 2px;
    border-radius: 0px;
    background: #fff;
    position: absolute;
    top: 0;
    bottom: 0;
    margin: auto;
    transition: opacity .15s;
}
.top-icon-w::before,
.top-icon-w::after {
    content: '';
    display: block;
    width: 100%;
    height: 2px;
    border-radius: 0px;
    background: #fff;
    position: absolute;
    left: 0;
    -webkit-transition: transform .2s;
    transition: transform .2s;
}
.top-icon-w::before {
    top: 0;
    -webkit-transform-origin: 0px 5px;
    transform-origin: 0px 5px;
}
.top-icon-w::after {
    bottom: 0;
    -webkit-transform-origin: 5px 0px;
    transform-origin: 5px 0px;
}

.menu-w.on .top-icon-w .icon-menu {
    opacity: 0;
}
.menu-w.on .top-icon-w::before {
    -webkit-transform: rotate(45deg);
    transform: rotate(45deg);
}
.menu-w.on .top-icon-w::after {
    -webkit-transform: rotate(-45deg);
    transform: rotate(-45deg);
}
.menu-w.on + .sub-nav-w {
    display: block;
}
.sub-nav-w {
    display: none;
    background: #fff;
    border-radius: 5px;
    box-shadow: 0 2px 10px #ddd;
    position: absolute;
    top: 55px;
    right: 10px;
    z-index: 2;
}
.sub-nav-w::before {
    content: '';
    width: 14px;
    height: 14px;
    background: #fff;
    border-radius: 2px;
    -webkit-transform: rotate(45deg);
    transform: rotate(45deg);
    position: absolute;
    top: -6px;
    right: 14px;
    z-index: 3;
}
.sub-nav {
    width: 170px;
}
.sub-nav li {
    position: relative;
}
.sub-nav li::after {
    content: '';
    display: block;
    width: 100%;
    height: 1px;
    background: #a5a5a5;
    -webkit-transform: scaleY(.3);
    transform: scaleY(.3);
    position: absolute;
    bottom: 0;
    left: 0;
}
.sub-nav li:last-child::after {
    display: none;
}
.sub-nav li a {
    height: 50px;
    line-height: 52px;
    font-size: 18px;
    padding: 0 14px;
    display: block;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.sub-nav li a img {
    display: inline-block;
    vertical-align: -2px;
    width: 20px;
    height: 20px;
    margin-right: 10px;
}
@media (max-width: 375px) {
    .sub-nav {
        width: 140px;
    }
    .iconfont {
        font-size: 20px;
        vertical-align: -1px;
        margin-right: 7px;
    }
    .sub-nav li a {
        font-size: 16px;
        height: 45px;
        line-height: 47px;
    }
}