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# Factorial

Let us practice the

`for`

loop with the
factorial used in mathematics.
The factorial of a positive integer n, denoted by n!, is the product of all positive integers less than or equal to n.
For example, 3! = 1*2*3 = 6. By definition, 0! = 1.## Exercise

Write a function

`factorial`

that calculates the factorial of a positive integer.
`factorial(3)`

should return `6`

.
+ Hint

```
var factorial = function(n) {
var result = 1;
for (...) {
...
}
return result;
};
```

+ Solution

```
var factorial = function(n) {
var result = 1;
for (var i = 1; i <= n; i++) {
result = result * i;
}
return result;
};
```