怎么才能让alert出现50啊
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>热身</title>
</head>
<body>
<p id="p1">我是第一段文字</p>
<p id="p2">我是第二段文字</p>
<script type="text/javascript">
function square(num){
var total=num*num;
return total;
}
var number=square(20)
var total=50;
alert(number);
</script>
</body>
</html>
