为什么要var num=0初始化值？num=num+ 为什么这里又要更新值？ 不理解望指点
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>while</title>
<script type="text/javascript">
var mynum =1;//mynum初值化数值为1
(mynum<=5)
{
document.write("数字:"+mynum);
mynum=mynum+1;
}
</script>
</head>
<body>
</body>
</html>
