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

[David .Wu]

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?