21 lines
623 B
Markdown
21 lines
623 B
Markdown
By definition, a factorial is `n!` can be written as `n * (n-1)!`.
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In other words, the result of `factorial(n)` can be calculated as `n` multiplied by the result of `factorial(n-1)`. And the call for `n-1` can recursively descend lower, and lower, till `1`.
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```js run
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function factorial(n) {
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return (n != 1) ? n * factorial(n - 1) : 1;
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}
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alert( factorial(5) ); // 120
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```
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The basis of recursion is the value `1`. We can also make `0` the basis here, doesn't matter much, but gives one more recursive step:
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```js run
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function factorial(n) {
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return n ? n * factorial(n - 1) : 1;
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}
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alert( factorial(5) ); // 120
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```
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