代码示例：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<script>
function jiecheng(a){
var b =1
for(;a>=1;a--){
b *=a
}
return b
}
var c = jiecheng(10)
console.log(c)
var d = jiecheng(12)
document.write(d)
</script>
</body>
</html>
代码示例：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<script>
function shulie(n){
if(n===1 || n===2) return 1
return shulie(n-1)+shulie(n-2)
}
var a=shulie(9)
console.log(a)
</script>
</body>
</html>
