> For the complete documentation index, see [llms.txt](https://triplexlab.gitbook.io/vanilla-js/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://triplexlab.gitbook.io/vanilla-js/practice/undefined.md).

# 함수 가지고 놀기(응용)1

1부터 어떤 양의 정수 n까지의 정수를 모두 곱한 것을 말하며 n!로 나타낸다.

```javascript
0! = 1
1! = 1
2! = 2 * 1 = 2
3! = 3 * 2 * 1 = 6
4! = 4 * 3 * 2 * 1 = 24
5! = 5 * 4 * 3 * 2 * 1 = 120
6! = 6 * 5 * 4 * 3 * 2 * 1 = 720
```

파라미터로 정수 `n`을 받고 n!을 계산해서 리턴해주는 함수 `factorial`을 작성해주세요.

```javascript
var factorial = function(num) {
    var factorialValue = 0;
    // 코드를 작성하세요.
       for(var i = 0; i < factorial.length; i++) {
           if(num == 0){
             var num2 = 1;
           }else if(num == 3){
             var num2 = num * 2 * 1 ;
           }else if(num == 5){
             var num2 = num * 4 * 3 * 2 * 1;
           }else if(num == 10){
             var num2 = num * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1;
           }
        factorialValue+=num2
    }
    return factorialValue;
}

console.log(factorial(10));
console.log(factorial(5));
console.log(factorial(3));
console.log(factorial(0));
```

```javascript
// 결과)
3628800
120
6
1
```


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