Javascript Skip Parâmetro padrão

function myfunc(x,y=2,z=6){
  console.log(x*y);
  console.log(z);
}
myfunc(5) //Output: 10 6
myfunc(5,4,2) //Output: 20 2
myfunc(5,undefined,17) //Output 10 17
Ugliest Unicorn