<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script type="text/javascript">
function showHobby(){
var hobbyObj=document.hobby.userHobby;
for(var i=0;i<hobbyObj.length;i++){
hobbyObj[i].checked=true;
}
}
function showHobby2(){
var hobbyObj=document.hobby.userHobby;
for(var i=0;i<hobbyObj.length;i++){
hobbyObj[i].checked=false;
}
}
function showHobby3(){
var hobbyObj=document.hobby.userHobby;
for(var i=0;i<hobbyObj.length;i++){
hobbyObj[i].checked=!hobbyObj[i].checked;
}
}
</script>
</head>
<body>
<form action="" name="hobby" method="get">
足球<input type="checkbox" name="userHobby" value="zu" />
<input type="button" value="全选" onclick="showHobby()"/>
<input type="button" value="不全选" onclick="showHobby2()">
<input type="button" value="反选" onclick="showHobby3()">
</form>
</body>
</html>
如上代码，为复选的全选全不选反选功能，当只有一个复选时三个功能都失效了
但将获取对象的代码var hobbyObj=document.hobby.userHobby;更换为
var hobbyObj=document.getElementsByName("userHobby");时，单个复选还可以用着三个功能，为什么呢？
