JavaScript委托并选择AJAX响应

How can I select a specific AJAX response using .html()?

Here is my HTML

<ul class="feature-products">       

</ul>
<div class="feature-btn">
    <a href="#" class="back styleShwd-enbl styleCrl-white stxt12">back</a> &nbsp;
    <a href="#" class="next styleShwd-enbl styleCrl-white stxt12">next</a>
</div>

Here is the AJAX response (inside my UL)

        <li class="products">                   
        .....
        </li>
        <li class="products">                   
        .....
        </li>
        <li class="products">
        .....
        </li>

Here is my script to select AJAX response (w/css animation)

$('.back').click(function() {        
    var back_indent = parseInt($('.feature-products').css('left')) + $(".products").outerWidth(true);              

    $('.feature-products').animate({"left":back_indent},200,function()
        {
            $('.feature-products li:first-child').css({'left':back_indent});
            $('.feature-products li:first-child').before($('.feature-products li:last-child')); 
        });       
    return false;
});

The problem is in the script, it can't select and get the value of back_indent, feature-products li:first-child.

i found my own solution. hope this page will help others.

first() & last() instead of :first-child & :last-child

$(".back").on('click', function(){      
    var back_indent = parseInt($('.feature-products').css('left')) + $(".products").outerWidth(true);       
    $('.feature-products').animate({"left":back_indent},200,function()
        {
        $(".feature-products li").first().css({'left':back_indent});
        $(".feature-products li").first().before($(".feature-products li").last());
        });             
    return false;       
});