[jQuery] Can I get the contents from respose by ajax

[jQuery] Can I get the contents from respose by ajax


I like to use $.ajax function when I need ajax
such as
$.ajax(
{
    url:'aa.php',
    cache:false,
    type:'get',
    data:{a:123},
    beforeSend:function()
    {
        //do something
    },
    success:function(res)
    {
        console.log(res);
    },
    error:function()
    {
        //do something
    }
});
res = responseText
if server transfer html code back like:
<div id='a'>123</div>
<div class='b'>456</div>
is there any way to get the value 123 straight from div?