SOURCE

$(()=>{
    $("input:button").click(()=>{
   let name=$("#name").val()
   let cls=$("#cls").val()
   let score=$("#score").val()

   let tr=$('<tr><td>'+getNum()+'</td><td>'+name+'</td><td>'+
   cls+'</td><td>'+score+'</td><td>'+'<button onclick="del(this)">删除</button></td></tr>')

   $('tbody').append(tr)
    })
})
function del(obj){

    $(obj).parent().parent().remove()
}

function getNum(){
     return $('tbody').children().length+1

}

<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<from>
    <input id="name" placeholder="姓名"/>
    <input id="cls" placeholder="班级"/>
    <input id="score"  placeholder="学号"/>
    <input type="button" value="添加"/>
</form>
<table border=1 cellspacing=0 cellpadding=5> 
    <thead> 
        <tr>
            <th>编号</th>
             <th>姓名</th>
             <th>班级</th>
            <th>成绩</th>
             <th>操作</th>
        </tr>
    </thead>
    <tbody></tbody>
</table>