Auto-arrange per Y value (position)

Based on the work by @Disposition_Dev and @femkeblanco, I wrote a more verbosely commented script and added the possibility to sort by any property. For sake of legibility, I used the JavaScript 'sort' function. I hope this helps.

function main() {
  // Check if there is an open document with a selection
  if (!app.documents.length) {
    alert("You must have a document open.");
    return;
  }

  var docRef = app.activeDocument;
  var sel = docRef.selection;

  if (!sel.length) {
    alert("You must make a selection.");
    return;
  }

  // Prompt the user for the sorting criterion
  var criterion = prompt("What property do you want to sort by? E.g. top, left, width, height, opacity, name:", "top");

  // If the property has a minus sign, the user wants to sort in reverse order. (*1)
  var sortOrder = 1;
  if (criterion[0] === "-") {
    sortOrder = -1;
    criterion = criterion.substr(1);
  }

  //  Make a copy of the array containing the selection:
  var items = [];
  for (var i = 0; i < sel.length; i++) {
    items.push(sel[i]);
  }

  // Sort the array by the criterion
  items = items.sort(dynamicSort(criterion));

  // iterate the array in reverse order while moving every element to the top:
  for (var i = items.length - 1; i >= 0; i--) {
    if (sortOrder === 1) {
      items[i].zOrder(ZOrderMethod.BRINGTOFRONT);
    } else {
      items[i].zOrder(ZOrderMethod.SENDTOBACK);
    }
  }
}

// Sorting function
function dynamicSort(property) {
  // Adapted from: https://stackoverflow.com/a/4760279/960592 (Credit: Ege Özcan)
  // (Adobe's Javascript doesn't seem to like double ternary operator)

  return function (a, b) {
    if (a[property] < b[property]) {
      return -1;
    }

    if (a[property] > b[property]) {
      return 1;
    }

    return 0;
  }
}


main();

/* 
Note: It *should* be possible to just reverse the array (items.reverse() ) or to change the sorting order in
the sorting function, but I couldn't get either method to work. This is a work-around.
*/