Swap Parameter Function Infinite Variable Return Possibility

Question

Say we have a function:
function swap(num1, num2) {
num1 += num2;
num2 = num1 - num2;
num1 -= num2;

return num1, num2;
}
Is it possible to do the following code:
var a = 3;
var b = 6;
var c = 5;
var d = 10;

swap(a, b); //a = 6, b = 3
swap(c, d); //c = 10, d = 5
swap(a, d); //a = 5, d = 6

Basically, is it possible to swap AS MUCH AS WANTED of the global variables by calling the function like that? I don't want to say:

function swap(num1, num2) {
//all code before

a = num1;
b = num2;
}

Because that will only change those 2 vars (a and b). I want it to be able to swap as many variables as are called. (a, b, c, q, x, y, z etc)

How do I make it possible?

Answer 1

I want to know how to change the values of global variables from inside a function.

Answer 2

Not sure about what the question is...
Could it be one of those:
(1) if the swap function always swap pairs, you can call the swap function as much as you want
(2) I if you want to pass an unknown number of parameters to the swap function, you will have to pass them as an array or a kind of list, then perform your "multiple swap" algorithm.
(look at the bubble sort algorithm as an example)