19 lines
420 B
Markdown
19 lines
420 B
Markdown
### factorial
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Calculates the factorial of a number.
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Use recursion.
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If `n` is less than or equal to `1`, return `1`.
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Otherwise, return the product of `n` and the factorial of `n - 1`.
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Throws an exception if `n` is a negative number.
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```js
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const factorial = n =>
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n < 0 ? (() => { throw new TypeError('Negative numbers are not allowed!'); })()
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: n <= 1 ? 1 : n * factorial(n - 1);
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```
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```js
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factorial(6) // 720
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```
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