JavaScript实现点击出现子菜单效果

<div class="menu">
 <div class="sign" id="sign"></div>
 <div class="lis" id="lis">
 <ul>
 <li><a href="">one</a></li>
 <li><a href="">two</a></li>
 <li><a href="">three</a></li>
 <li><a href="">four</a></li>
 <li><a href="">five</a></li>
 </ul>
 </div>
</div>

ul{
 padding-inline-start: 0px;
 }
 .menu{
 margin: 0 auto;
 background:#0DA795;
 height: 40px;
 width: 600px;
 }
 .sign{
 width: 30px;
 float: right;
 margin-right: 20px;
 margin-top: 8px;
 height: 25px;
 background: rgba(243,193,63,1.00);
 border-radius: 5px;
 position: relative;
 cursor: pointer;//把光标设置成手的形状
 }
 .lis{
 position: absolute;
 top:30px;
 display: none;
 }
 .lis ul li{
 list-style: none;
 width: 600px;
 line-height: 40px;
 font-size: 14px;
 text-align: center;
 border-bottom: 1px solid #565656;
 background:#EAEDD5;
 }.lis a{
 text-decoration: none;
 color: black;
 }
 .lis a:hover{
 color: #0da759;
}

<script>
 var biaozhi=document.getElementById("sign");
 var li=document.getElementById("lis");
 biaozhi.onclick=function(){
 var i=li.style.display;
 if (i=="none"){
 li.style.display="block";//第一条语句
 }else{
 li.style.display="none";//第二条语句
 }
 }
</script>