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                            /JavaScript
                        
                        /JavaScript进阶篇

<!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();">
<input type="button" value = "反选" onclick = "fanxuan();">

<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");

// 任务1
for(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
var hobby = document.getElementsByName("hobby");
for(i = 0;i < hobby.length;i++){
hobby[i].checked = false;
}
}

function checkone(){
var j=document.getElementById("wb").value;

// 任务3
var hobby = document.getElementById("hobby"+j);
hobby.checked = true;

}

</script>
</body>

</html>

含反选代码！