Part of developing (and certainly learning to develop) is creating code, commenting it out, and creating a better version. As you get into a flow state with coding it’s really easy to get into the habit of doing this and not going back and clearing out the undead code comments.

Here’s an example of what I’m talking about.

function thriller() {
  return “Something evil\'s lurking from the dark”;
}

//function funkyTown() {
//  chargeKeytar();
//  dressInPastels();
//  return “Gotta make a move to a town that\'s right for me”;
//}
//funkyTown();

thriller();

The trouble with code like this is it’s not clear why the commented out code is there. Is the intention to reworking and use it? Can we remove this because the code was old? Was it commented out accidentally?

Zombie code is ambiguous code, and that’s not helpful for anyone. It’s fine in your own dev environment in the short term, but don’t leave it in too long and never let the zombie out in public. It will only eat everyone’s brains.