Looking to select all items on the layer "Text Layer" and then run pathfinder subtract

So, what happens if you replace

var f = page.pageItems.everyItem().getElements();

with

var f = page.allPageItems;

in the script above? If you see the reverse of what you expect, then reverse the array by using  unshift() instead of push(): replace

a.push (f[i]);

with

a.unshift (f[i]);

Which of course is pretty whacky. You could also try a different pathfinder method (minusBack(), intersectPath(), etc.).

P.

Stacking order is elusive. It was discussed in this forum some years ago, and its behaviour changed at some stage. An experiment now shows that pageItems and allPageItems show different behaviour w.r.t. stacking order. Take this situation:

Two rectangles and two text frames. The 0 and 1 suffixes denote the order of creation. The frames in the screenshot were moved around a bit (order of creation was texxt frame 0, text frame 1, rectangle 0, rectangle 1).

This script:

items = app.documents[0].pageItems.everyItem().getElements();
for (i = 0; i < items.length; i++) {
  $.writeln (items[i].name + ' -- ' + items[i].index);
}

prints this in the console:

rectangle 1 -- 0

rectangle 0 -- 1
text frame 0 -- 0
text frame 1 -- 1

That is, no matter the creation order, the order is the order in the Layers panel but grouped by item type: rectangles before text frames.

However, this script

items = app.documents[0].allPageItems;
for (i = 0; i < items.length; i++) {
  $.writeln (items[i].name + ' -- ' + items[i].index);
}

prints the items in the order shown in the Layers panel:

text frame 0 -- 0
rectangle 1 -- 0
text frame 1 -- 1
rectangle 0 -- 1

After some test, i think that the problem is the order of the elements of the array.

Given three objects (Rectangle (white frame), polygon (outlined text), textFrame) it doesn’t matter how they are stacked in the ‘Text Layer’, their order in the array is always the same: rectangle, polygon, textframe. 

You have to rearrange the array and then the script works.

function textLayerFrames (page) {
  var f = page.pageItems.everyItem().getElements();
  var a = [];
  for (var i = 0; i < f.length; i++) {
    if (f[i].itemLayer.name === 'Text Layer') {
      a.push (f[i]);
    }
  }
  alert(a);
  var b = [];
  b.push(a[2]);
  b.push(a[1]);
  b.push(a[0]);
  alert(b);
  return b;
}

pages = app.documents[0].pages.everyItem().getElements();
for (i = 0; i < pages.length; i++) {
  frames = textLayerFrames (pages[i]);
  frames[0].subtractPath (frames);
}

Robert is probably right: it's a matter of the stacking order of the objects and how a script orders the objects. Can you show the content of the text layer? Is the image on that layer or somewhere else? Maybe post your document (or a small representative sample).

Actually, try replacing subtractPath with excludeOverlapPath and see whether makes a difference.

As Brian and Robert mentioned, you need to work page by page. On each page get the frames on the text layer, then use InDesign's subtractPath() method:

function textLayerFrames (page) {
  var f = page.pageItems.everyItem().getElements();
  var a = [];
  for (var i = 0; i < f.length; i++) {
    if (f[i].itemLayer.name === 'Text Layer') {
      a.push (f[i]);
    }
  }
  return a;
}

pages = app.documents[0].pages.everyItem().getElements();
for (i = 0; i < pages.length; i++) {
  frames = textLayerFrames (pages[i]);
  frames[0].subtractPath (frames);
}

 You're not working with any selection here. Working with selections should really be avoided as much as possible, working with script functions such as subtractPath() are much more robust.

P.

If the items are on multiple pages, select won't work. Instead iterate through the items and select individually.