Javascript, calculating factorial

The factorial of a given positive integer is the product of all positive integers less than and equal to the given positive integer. For example, the factorial of 5!=1*2*3*4*5=120
The javascript code snippet below demonstrates two methods of calculating the factorial of a number, recursive and iterative.
[code language=”javascript”]
function recursiveFactorial(num)
{
if(num < 0) {
return -1;
}
else if(num === 0) {
return 1;
} else {
return num * recursiveFactorial(num-1);
}
}

function iterativeFactorial(num)
{
if (num < 0) {
return -1;
}
else if (num === 0) {
return 1;
}

var factorial = num;
num = num-1;
while (num > 1) {
factorial = factorial * num;
num = num -1;
}
return factorial;
}

console.log( "The factorial of 5 is:", recursiveFactorial( 5 ) );
console.log( "The factorial of 5 is:", iterativeFactorial( 5 ) );
[/code]

Output:
[code language=”text”][/code]
The factorial of 5 is: 120
The factorial of 5 is: 120
[code][/code]