Create a variadic function that uses function's arguments as variables.

variadic.js

(function(x, y, z) {
  "use strict";
  
  x = y = 0;
  z = arguments.length;
  
  for (; y < z; y++) {
    x += arguments[y];
  }
  
  return x;
})(6,5,4,3,2,1);
// 21