checkBox 兑现全选 _Web前端

checkBox 实现全选
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	<script type="text/javascript" language="javascript">
		function selectedAll(){
			var checkBoxStatus = document.getElementById("QueryAll").checked;
			var inputObj = document.getElementsByTagName('input');
			for(var i=0;i<inputObj.length;i++){
				if(inputObj[i].type == "checkbox"){
					inputObj[i].checked = checkBoxStatus;
				}
			}
		}
	</script>    
  </head>
  
  <body>
  	<input type="checkbox" name="checkboxmain" id="QueryAll" onclick="javascript: selectedAll()"/><BR/>
	<input type="checkbox" id="checkboxname" /> 中国<BR/>
	<input type="checkbox" id="checkboxname" /> 美国
  </body>
  
</html>