javascript

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>


Solution

  • 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;
    }