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全选把false改成true不行吗

function clearall(){
var hobby = document.getElementsByName("hobby");

// 任务2
for(i=0;i<hobby.length;i++){
hobby[i].checked=false;
}
}

全选把false改成true不行吗

现实_不允许

2015-07-15

源自：JavaScript进阶篇 9-4

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1 回答

arlenhui
2015-07-15

<!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 j=document.getElementById("wb").value;
            var hobby = document.getElementsByName("hobby");
        switch(j)
        {
            case "1":
                hobby[0].checked=true;
                break;
            case "2":
                hobby[1].checked=true;
                break;
                case "3":
                hobby[2].checked=true;
                break;
                case "4":
                hobby[3].checked=true;
                break;
                case "5":
                hobby[4].checked=true;
                case "6":
                hobby[5].checked=true;
                break;
        }
         // 任务3
        
        }
        
        </script>
    </body>
</html>