js 模仿锚点定位的实现方法

<div class="designer-bg ov">
<div class="w-77 f-l designer-nav">
    <ul id="scroll_nav">
     <li class="designer-nav-li"><a href="" title="" data-nav="a">A - E</a></li>
     <li class="designer-nav-li"><a href="" title="" data-nav="f">F - L</a></li>
     <li class="designer-nav-li"><a href="" title="" data-nav="m">M - T</a></li>
     <li class="designer-nav-li"><a href="" title="" data-nav="u">U - Z</a></li>
    </ul>
</div>
                                <script type="text/javascript">
$(function(){
    var navLinks = $(&#39;#scroll_nav&#39;).find(&#39;a&#39;) , target_ul = $(&#39;#designer_nav_name&#39;) , _top = 0;
    $.each(navLinks , function( i , elem ){
        $(elem).attr(&#39;data-to&#39; , i == 0 ? 0 : _top);
        var id = $(elem).attr(&#39;data-nav&#39;);
        var _h4 = $(&#39;#&#39;+id).parent();
        _top = parseInt(_h4.next().height()) + _top + parseInt(_h4.height());
         
        $(elem).bind(&#39;click&#39;, function(){
            target_ul[0].scrollTop = $(this).attr(&#39;data-to&#39;);
            return false;
        });
    });
    $(&#39;#designer_nav_name li&#39;).click(function( e ){
        var designer_name_href= $(this).find(&#39;a&#39;).attr("href"); 
        $.getJSON("test.php?action=test&jsoncallback=?&testid="+testidhref,function(data){
            $(&#39;#Ttai&#39;).html(data.catwalk);
        });
        e.preventDefault();
    });
})
                                </script>
<div class="f-r designer-index" id="designer_nav_name">
                                 
<h4><a name="a" id="a"><strong>A</strong></a></h4>
<ul>
<li></li>
</ul>
<h4><a name="f" id="f"><strong>F</strong></a></h4>
<ul>
<li></li>
</ul><h4><a name="m" id="m"><strong>M</strong></a></h4><ul>
<li></li>
</ul><h4><a name="u" id="u"><strong>U</strong></a></h4><ul>
<li></li>
</ul>
</div> </div>