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1-js/06-advanced-functions/01-recursion/02-factorial/solution.md

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+By definition, a factorial is `n!` can be written as `n * (n-1)!`.
+
+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`.
+
+```js run
+function factorial(n) {
+  return (n != 1) ? n * factorial(n - 1) : 1;
+}
+
+alert( factorial(5) ); // 120
+```
+
+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:
+
+```js run
+function factorial(n) {
+  return n ? n * factorial(n - 1) : 1;
+}
+
+alert( factorial(5) ); // 120
+```