js来添加重复的输入框

HTML代码：

     <div style="margin-top:60px;" id="pic_setting">
               <span style="font-family:Arial;font-size:13px;font-weight:bold;">默认轮播大图设置：</span>
               <div id="pic_div_contain">
                    <div class="pic_div_num" id="entry_1">
                         <p style="padding-left:15px;padding-top:20px;">
                              <span id="pic_num_1">1</span><span style="padding-left:10px;padding-right:10px;">图片地址</span>
                              <input id="pic_url_1" type="text" name="pic_url[]" style="width:375px;height:25px;margin-right:10px;"/>
                              <a href="javascript:void(0)" onclick="viewPic(1);return false;">预览</a>
                              <a href="javascript:void(0)" onclick="delPic(1);return false;">删除</a>
                         </p>
                         <p style="padding-left:15px;padding-top:10px;">
                              <span style="padding-left:17px;padding-right:10px;">链接地址</span>
                              <input id="link_url_1" type="text" name="link_url[]" style="width:375px;height:25px;"/>
                         </p>
                    </div>    
               </div>
                   
               <p style="padding-left:420px;padding-top:10px;"> <a href="#" onclick="addRoundPic();return false;">添加大图</a></p>
          </div>

JS代码：

     function addRoundPic() {

     var pre_id = $('#pic_div_contain .pic_div_num:last').attr('id');
    if ($('#pic_div_contain .pic_div_num').length >= 10 ) {
         $('#actionLayer').show();
          $("#actionLayer").css('left', (($(document).width()) / 2 - (parseInt(355) / 2)) + 'px');
          $('#actionHint').html('条目数最大为10条！');
          return false;
    } else {
        var _num = pre_id.indexOf('_');
        var entry_num = parseInt(pre_id.substr(_num+1))+1;
        var $html ='\
               <div class="pic_div_num"  id="entry_' + entry_num + '">\
                    <p style="padding-left:15px;padding-top:20px;">\
                         <span id="pic_num_' + entry_num + '">' + entry_num + '</span><span style="padding-left:10px;padding-right:10px;">图片地址</span>\
                         <input id="pic_url_' + entry_num + '" type="text" name="pic_url[]" style="width:375px;height:25px;margin-right:10px;"/>\
                         <a href="javascript:void(0)" onclick="viewPic(' + entry_num + ');return false;">预览</a>\
                         <a href="javascript:void(0)" onclick="delPic(' + entry_num + ');return false;">删除</a>\
                    </p>\
                    <p style="padding-left:15px;padding-top:10px;">\
                         <span style="padding-left:17px;padding-right:10px;">链接地址</span>\
                         <input id="link_url_' + entry_num + '" type="text" name="link_url[]" style="width:375px;height:25px;"/>\
                    </p>\
               </div>';
        $('#pic_div_contain').append($html);
        pre_id = "entry_"+entry_num;
    }
}