JavaScript 实现仿锚点平滑滚动定位

<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 = $('#scroll_nav').find('a') , target_ul = $('#designer_nav_name') , _top = 0;
	$.each(navLinks , function( i , elem ){
		$(elem).attr('data-to' , i == 0 ? 0 : _top);
		var id = $(elem).attr('data-nav');
		var _h4 = $('#'+id).parent();
		_top = parseInt(_h4.next().height()) + _top + parseInt(_h4.height());
		
		$(elem).bind('click', function(){
			target_ul[0].scrollTop = $(this).attr('data-to');
			return false;
		});
	});
	$('#designer_nav_name li').click(function( e ){
		var designer_name_href= $(this).find('a').attr("href");	
		$.getJSON("test.php?action=test&jsoncallback=?&testid="+testidhref,function(data){
			$('#Ttai').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>