比如：<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>变量</title>
<script type="text/javascript">
var mynum=8;
document.write(mynum);//printf mynum's value
</script>
</head>
<body>
</body>
</html>和这个<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>变量</title>
<script type="text/javascript">
var mynum;
mynum="javascript";
mynum="8";
document.write(mynum);
</script>
</head>
<body>
</body>
</html>
怎么都写的不同呢！
