html select 下拉框ajax 请求

<meta charset="utf-8">

<select class="field" name="test" >
<option value="1">信息一</option>
<option value="2" selected="selected">信息二</option>
<option value="3">信息三</option>
<option value="4">信息四</option>
</select>

<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
<script type="text/javascript">

$(".field").change(function(){
var id = $(".field option:selected").val();
$.ajax({
dataType :'json',
type : "POST",
url : "11.php",
data : {
"id" : id

},

success : function(data) {
if(data.code==200){
alert(data.msg);
// location = "/index";
}else{
alert(data.msg);
// return;

}
},
error : function(data) {
alert(data.msg);

}
});

});

</script>