我尝试在变量后面输入 空格符号，为什么所有内容清空呢
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>document.write</title>
<script type="text/javascript">
var mystr="我是";
var mychar="JavaScript";
document.write(mychar+"<br>");
document.write(mystr+mychar+" 的忠实粉丝！");//正常
document.write(mystr+  mychar+" 的忠实粉丝！"//清空
</script>
</head>
<body>
</body>
</html>
