JavaScript DOM实现复选框全选、全清与反选功能

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>复选框全选全清和反选</title>
<script type="text/javascript">
//取得所有的复选框对象数组
function GetAllCheckBox() {
  var div = document.getElementById("Balls");
  var inputs = div.getElementsByTagName("input");
  //定义复选框数组，用来返回
  var checkboxs = new Array();
  var nIndex = 0;
  for (var i = 0; i < inputs.length; i++) {
 //通过type是否为checkbox来判断复选框
 if (inputs[i].type == "checkbox") {
   checkboxs[nIndex] = inputs[i];
   nIndex++;
 }
  }
  return checkboxs;
}
//全选
function selAll() {
  var checkboxs = GetAllCheckBox();
  for (var i = 0; i < checkboxs.length; i++) {
 checkboxs[i].checked = true;
  }
}
//全清
function clearAll() {
  var checkboxs = GetAllCheckBox();
  for (var i = 0; i < checkboxs.length; i++) {
 checkboxs[i].checked = false;
  }
}
//反选
function reverseAll() {
  var checkboxs = GetAllCheckBox();
  for (var i = 0; i < checkboxs.length; i++) {
 if (checkboxs[i].checked == true) {
   checkboxs[i].checked = false;
 }
 else {
   checkboxs[i].checked = true;
 }
  }
}
</script>
</head>
<body>
<div id="Balls">
<input type="checkbox" id="c1" /><label for="c1">足球</label>
<input type="checkbox" id="c2" /><label for="c2">台球</label>
<input type="checkbox" id="c3" /><label for="c3">乒乓球</label>
<br />
<input type="button" value="全选" onclick="selAll()" />
<input type="button" value="全清" onclick="clearAll()" />
<input type="button" value="反选" onclick="reverseAll()" />
</div>
</body>
</html>