                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript进阶篇

求助！！！！

<!DOCTYPE HTML>
<html>

   <head>
       <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
       <title>无标题文档</title>
   </head>

   <body>
       <form>
           请选择你爱好:<br>
           <input type="checkbox" name="hobby" id="hobby1"> 音乐
           <input type="checkbox" name="hobby" id="hobby2"> 登山
           <input type="checkbox" name="hobby" id="hobby3"> 游泳
           <input type="checkbox" name="hobby" id="hobby4"> 阅读
           <input type="checkbox" name="hobby" id="hobby5"> 打球
           <input type="checkbox" name="hobby" id="hobby6"> 跑步 <br>
           <input type="button" value="全选" onclick="checkall();">
           <input type="button" value="全不选" onclick="clearall();">
           <p>请输入您要选择爱好的序号，序号为1-6:</p>
           <input id="wb" name="wb" type="text">
           <input name="ok" type="button" value="确定" onclick="checkone();">
       </form>
       <script type="text/javascript">
           function checkall() {
               var hobby = document.getElementsByTagName("input");
               for(var i = 0; i < hobby.length; i++) {
                   hobby[i].checked = true;
               }
               // 任务1

           }

           function clearall() {
               var hobby = document.getElementsByName("hobby");
               for(var i = 0; i < hobby.length; i++) {
                   hobby[i].checked = false;
               }
               // 任务2

           }

           function checkone() {
               var hobby = document.getElementsByName("hobby");
               var j = document.getElementById("wb").value;
               for(var j = 0; j < hobby.length; j++) {
                   hobby[j - 1].checked = true;

               }
               // 任务3

           }
       </script>
   </body>

</html>