factorial (n!) bench: http://jsperf.com/factorial-test-my/2

factorial.js

function fact1(x) {
	if(x<=1) return 1;
	else return x*fact(x-1);
}


function fact2(x){
   var res=x;
   while(--x){
      res *= x;
   }
   return res;
}

//best performance
function fac1(x)
{
  var r = 1;
  for(var i=2;i<=x;i++)
  {
    r *= i;
  }
  return r;
}