<!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>无标题文档</title>
</head>
<body>
</body>
</html>
<script>
/*输入一个数，求阶乘之和*/
var n=prompt("请输入一个整数");
if(n==null)
{}
else
{
var e=isNaN(n);
if(e==false)
{
var f=parseInt(n);
var g=1;
var sum=0;
for(var i=1;i<=f;i++)
{
g*=i;
sum+=g;
}
document.write(sum);
}
else
{
alert("输入有误！");
}
}
</script>