html代码：
<div class="dropdownContainer">
<div class="dropdownDefault">1</div>
<span class="downArrow arrow"></span>
<ul class="dropdrown-menu">
<li><a href="#">1</a></li>
<li><a href="#">2</a></li>
<li><a href="#">6</a></li>
<li><a href="#">8</a></li>
</ul>
</div>
css代码：
.dropdownContainer{position: relative;height: 30px;width: 100%;background: #555;}
.dropdownDefault{border:1px solid #ddd;line-height: 28px;text-indent: 0.5em;}
.dropdownContainer .downArrow{position: absolute;right: 5px;top: 9px}
.dropdrown-menu{position: absolute;top:100%;width: 100%;left: 0;background: #555;display: none;}
.dropdrown-menu li{line-height: 24px;}
.dropdrown-menu li a{display: inline-block;width: 100%;text-indent: 0.5em}
.dropdrown-menu li a:hover{background: #0078b6;font-size: 1.1em;}
.arrow{width: 0;height: 0;display: inline-block;cursor: pointer;}
.downArrow{border-left: 6px solid transparent;border-right: 6px solid transparent;border-top: 12px solid #fff;}
js(jquery)代码：
$(".dropdownDefault,.dropdownContainer .downArrow").click(function(){
$(this).siblings(".dropdrown-menu").show();
});
$(".dropdrown-menu li a").click(function(){
$(this).parent().parent().siblings(".dropdownDefault").html($(this).html());
$(this).parent().parent().hide();
});
虽然代码很简单，但是效果是不是非常酷呢