都不出来~~~好难过呀~~哪的问题呀
<!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++){
                    if(hobby[i].type=="checkbox"){
                    hobby[i].checked=true;   
                    }               
                }
            }
        function clearall(){
            var hobby = document.getElementsByName("hobby");
            
         // 任务2    
         for(var i=0;i<hobby.length;i++){
             hobby[i].checked=false;
         }
            
        }
        
        function checkone(){
            var j=document.getElementById("wb").value;
        
         // 任务3
         if(j>0&&j<=6) 
         document.getElementById("hobby"+j).checked=true;
        }
        else alert("请输入1-6的值");
        
        </script>
    </body>
</html>

 
                            