其实我今天想到了一个更好的办法
<select id="test" onclick="test()">
<option value="1">测试一</option>
<option value="2">测试二</option>
<option value="3">测试三</option>
<option value="4">测试四</option>
</select>
<script>
var click_num = 0;
function test(){
click_num = click_num + 1;
if(click_num == 2){
click_num = 0;
alert($('#test').val());
}
}
</script>