JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu">
    <ul>
        <li class="active">
            <a href="?l=EL&amp;m=932K59EciV">Menu #1</a>
        </li>
        <li>
            <a href="?l=EL&amp;m=M-z-3crmAP">Menu #2</a>
        </li>
        <li>
            <a href="?l=EL&amp;m=jpHiTwH1bT">Menu #3</a>
        </li>
        <li>
            <a href="?l=EL&amp;m=Jwr0SIWoWX">Menu #4</a>
        </li>
        <li>
            <a href="?l=EL&amp;m=QY8SgMl5JH">Menu #4</a>
        </li>
        <li>
            <a href="?l=EL&amp;m=8GaCmPByu3">Menu #5</a>
        </li>
        <li>
            <ul>
                <li>
                    <a href="?l=EL&amp;m=ueHp2vYKUa">Submenu #1</a>
                </li>
                <li>
                    <a href="?l=EL&amp;m=HQvyKxum8q">Submenu #2</a>
                </li>
                <li>
                    <a href="?l=EL&amp;m=81cDaTOCsL">Submenu #3</a>
                </li>
            </ul>
            <a href="?l=EL&amp;m=BQMppfQ0Dl">Menu #6</a>
        </li>
        <li>
            <a href="?l=EL&amp;m=D3wTd4F5Mn">Menu #7</a>
        </li>
    </ul>
</div>

CSS

#menu ul {
    width: 160px;
    padding: 4px;
    margin: 0;
    border: 2px solid #94AA13;
    background-color: #fff;
    border-radius: 4px;
}

#menu li {
    position: relative;
    padding: 0;
    margin: 0;
}

#menu li + li {
    margin-top: 4px;
}

#menu a {
    display: block;
    padding: 0 20px;
    font-size: 14px;
    line-height: 36px;
    color: #f2f2f2;
    background-color: #283720;
    border-radius: 4px;
}

#menu li > ul {
    display: none;
    position: absolute;
    top: 0;
    left: 100%;
    margin: -4px 0 0 10px;
}

#menu li:hover > ul {
    display: block;
}

#menu li:hover > ul:before {
    display: block;
    content: "";
    position: absolute;
    top: 0;
    left: -16px;
    width: 16px;
    height: 100%;
}

#menu a:hover, #menu li.active > a {
    background-color: #3B753A;
    color: #fff;
}

#menu ul + a {
    background-image: url("http://cdn1.iconfinder.com/data/icons/circular%20icons/arrow_right.png");
    background-position: right;
    background-repeat: no-repeat;
}