<style>
html, body {
margin: 0;
padding: 0;
}
.btn-group{
font-size: 14px;
position: relative;
}
.open>.dropdown-menu{
display: block;
}
.btn{
padding: 10px 30px;
border: 1px #E8940B solid;
background: #f1f1f1;
}
.dropdown-menu{
position: absolute;
left: 0;
z-index:1000;
display: none;
min- 160px;
padding: 5px 0px;
margin: 5px 0px;
border: 1px #438FF5 solid;
text-align: center;
list-style: none;
background: white;
}
.dropdown-menu>li{
line-height:35px;
white-space:nowrap;
}
</style>
<body>
<div class="btn-group open">
<button class="btn btn-toggle">按钮</button>
<ul class="dropdown-menu">
<li>上海上海1</li>
<li>中国中国2</li>
<li>哈尔冰3</li>
<li>生日快乐4</li>
<li>节日快乐5</li>
</ul>
</div>
</body>