factorial of a number

I have the following code but it is not giving perfect result for factorial. Can you find it out please?

function fact(num) {
  var x = parseInt(num);
  if (x > 0)
    x = x * fact(x - 1);
  console.log(x);
}

<form name="f1">
  Enter the Number :<input type="text" length="8" name="txt1"><br>
  <input type="button" value="Find factiorial" onclick="fact(txt1.value)">
</form>

You have to return the value. Here you go:

function fact(x) {
   if(x==0) {
      return 1;
   }
   return x * fact(x-1);
}

function run(number) {
    alert(fact(parseInt(number, 10)));
}

and

<input type="button" value="Find factiorial" onclick="run(txt1.value)">

(How to make it work for negative numbers I leave up to you ;) (but I showed in this post anyway))

Just for fun, a more correct, non recursive algorithm:

function fact(x) {
       if(x == 0) {
           return 1;
       }
       if(x < 0 ) {
           return undefined;
       }
       if(x === Infinity){
           return Infinity
       }
       for(var i = x; --i; ) {
           x *= i;
       }
       return x;
}