Most efficient way to write Combination and Permutation calculator in Javascript

Question

I have a math website http://finitehelp.com that teaches students Finite Math. I thought it would be cool to include a calculator so I made one for combinations and permutat

Answer 1

If you're concerned about efficiency, you'd probably want to re-implement the factorial as an iterative function rather than a recursive one. The recursive version will use a lot more memory and CPU time than the iterative version.

function factorial(n) { 
  var x=1; 
  var f=1;
  while (x<=n) {
    f*=x; x++;
  }
    return f;
}

You also shouldn't be adding your own functions to the Math namespace. It's not a good habit to get into.