js动态添加表格行

参考了N多代码后实现的：

效果：点击添加按钮，向下添加一行，上一条操作变为删除

js代码

<script>
$(function(){
    addonetr();
});
function addonetr(){
    $($("#table2 tbody")[0]).append("<tr><td align='center'>"+
        "<select name='types'><option value=''>请选择</option>"+
        "<option value='0'>单选题</option>"+
        "<option value='1'>多选题</option>"+
        "<option value='2'>问答题</option></select></td>"+
        "<td align='center'><input type='text' size='45' value='' name='ques'/></td>"+
        "<td align='center'><input type='text' size='45' value=''name='answ'/></td>"+
        "<td align='center'><button name='delButton' οnclick='deltr(this);' class='btn1'>删除</button>"+
        "<button name='addButton' οnclick='addonetr();' class='btn1'>添加</button></td></tr>");
  
    $("button[name='delButton']").each(function(){
        $(this).attr("style","display:block;");
    });
    $("button[name='delButton']:last").each(function(){
        $(this).attr("style","display:none;");
    });
    $("button[name='addButton']").each(function(){
        $(this).attr("style","display:none;");
    });
    $("button[name='addButton']:last").each(function(){
        $(this).attr("style","display:block;");
    });
    try{event.returnValue=false;}
    catch(e){}
};
//删除行的函数，必须要放domready函数外面
function deltr(delbtn){
    $($(delbtn).parents("tr")[0]).remove();
};
</script>

html代码

<div>
    <form action="" method="post">
    <table width="100%" border="0" cellspacing="0" cellpadding="0">    
        <tr>
            <td width="100" height="35"  align="right" valign="top" >问卷标题:</td>
            <td><input id="title3" type="text" name="title" size="70"/></td>
        </tr>
        <tr>
            <td width="100" height="35"  align="right" valign="top" >发起单位:
            </td>
            <td><input type="text" name="title" size="70" id="initiator"/></td>
        </tr>
        <tr>
            <td width="100" height="35"  align="right" valign="top" >问卷介绍:
            </td>
            <td><textarea rows="5" cols="100" name="context" id="descirbes"></textarea></td>
        </tr>
        <tr><td><br/></td></tr>
        <tr><td><br/></td></tr>
        <tr>
            <td width="100" height="35"  align="right" valign="top">问卷内容:
            </td>
            <td>
                <table id="table2" border="1" border="0" cellspacing="0" cellpadding="0" width="89%">
                    <tbody>
                    <tr>
                        <td align="center" width="8%">题型</td>
                        <td align="center" width="24%">问题</td>
                        <td align="center" width="24%">答案</td>
                        <td align="center" width="8%">操作</td>
                    </tr>
                    
                    </tbody>
                </table>
        
    </table>
    </form> 
</div>