# Calculate the factorial of a number

Multiply the integers from 1 to n recursively.

Canonical: https://1loc.dev/number/calculate-the-factorial-of-a-number/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function factorial(n) { return n <= 1 ? 1 : n * factorial(n - 1); }
```

## Input

```json
5
```

## Expected output

```json
120
```

## Edge case

Input:
```json
0
```
Output:
```json
1
```

## Limits

- The lab stops at 18: 19! exceeds Number.MAX_SAFE_INTEGER. Use BigInt for larger values.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/calculate-the-factorial-of-a-number.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Caps n at 18 to stay below Number.MAX_SAFE_INTEGER. Original MDX retained as inert source evidence.