无样式，比较丑
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<script>
window.onload=function(){
var arr=document.getElementsByName("a");
//全选
var btn=document.getElementsByName("b")[0];
btn.onclick=function(){
for(var i=0; i<arr.length; i++){
arr[i].checked=this.checked;
}
}
//反选
var btn2=document.getElementsByName("c")[0];
btn2.onclick=function(){
for(var i=0; i<arr.length; i++){
arr[i].checked = !arr[i].checked;
}
}
//取出所选值
var btn3=document.getElementsByName("d")[0];
btn3.onclick=function(){
var str="";
for(var i=0; i<arr.length; i++){
if( arr[i].checked ){
str+=arr[i].value+"; "
}
}
alert(str);
}
/*
!指取反，返回布尔类型
*/
}
</script>
</head>
<body>
<input type="checkbox" name="a" value="1" />1
<input type="checkbox" name="a" value="2" />2
<input type="checkbox" name="a" value="3" />3
<input type="checkbox" name="a" value="4" />4
<br>
<input type="checkbox" name="b" />全选
<br>
<input type="button" name="c" value="反选" />
<br>
<input type="button" name="d" value="取出所选值" />
</body>
</html>