joonaspaakko

// Select Next Layer (invisible or not).jsx
// https://gist.github.com/joonaspaakko/048c9b58ccbb6e6f44c894bf4ce30b68

nextLayer('down');

// direction (↑): "up" or "above"
// direction (↓): "down" or "below"
function nextLayer( direction ) {
  
  var doc = app.activeDocument;