我去掉numa，numb的赋值，也能运行成功？为毛？
逻辑与
我去掉numa，numb的赋值，也能运行成功？为毛？
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>逻辑与</title>
<script type="text/javascript">
var numa,numb;
if(numa>=60 && numb>=60 )
{
document.write("JavaScript考核通过！"+"<br>");
}
</script>
</head>
<body>
</body>
</html>
