JavaScript implementation method to convert UPC to ISBN

This article describes the JavaScript implementation method of converting UPC to ISBN. Share it for your reference. The specific implementation method is as follows:

if (("978") == 0) {
  isbn = (3,9);
  var xsum = 0;
  var add = 0;
  var i = 0;
  for (i = 0; i < 9; i++) {
    add = (i,1);
    xsum += (10 - i) * add;
  }
  xsum %= 11;
  xsum = 11 - xsum;
  if (xsum == 10) { xsum = "X"; }
  if (xsum == 11) { xsum = "0"; }
  isbn += xsum;
}

I hope this article will be helpful to everyone's JavaScript programming.