document.write("mynum"+mynum);括号中变量字符串加“”与不加的结果，变量的结果不一样，什么原理呢，谢谢
<!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";
var mynum=8;
document.write("mynum"+mynum);
</script>
</head>
<body>
</body>
</html>
