ID Scripting: PageItems on Layer: collection 'pageItems' and flat array 'allPageItems' are empty.

Thanks Uwe, or maybe loop the document page items and check the page item’s parent and itemLayer name?

var doc = app.documents.item(0);
var ln = "erh_w_test"
var lpi = getMPLayerItems(ln)
$.writeln("The are " + lpi.length + " page items in the layer named " + ln + " on the masters")

/**
* Gets the page items on master spreads in the specified layer 
* @9397041 the name of the layer to check
* @Return an array of page items 
* 
*/
function getMPLayerItems(n){
    var a = new Array
    var pi = doc.pageItems;
    var i = pi.length; while (i--) if (pi[i].parent.constructor.name == "MasterSpread" && pi[i].itemLayer.name == n) a.push(pi[i]);
    return a
}

Rob Day,

Unfortunately, the script logic does not allow using overriding master pageitems at the time of processing. The use of a layer was necessary only for logical grouping these master pageitems for fast processing without loops.  (Filtering pageitems doesn't make the task much harder).

The fact is that this auxiliary layer was conceived exclusively for working on master spreads.

There was also an idea to use Groups, but their action is limited to only one masterSpread.

So far,  not very long code like this will do fine.

Array.prototype.filter = function(f) {
	var i = -1, l = this.length;
	
	if ('function' == typeof f) {
		while (++i < l) {
			(!f.apply(this, [this[i], i, this])) && this.splice(i, 1);
		}
	}
        return this;
}
/////////
Layer.prototype.findAllMasterPageItems = function() {
	var that = this;
	
	return app.activeDocument.masterSpreads.everyItem().pageItems.everyItem().getElements()
	.filter(function(pi){
		return pi.itemLayer === that;
	});
}

////////

var lmpi = app.activeDocument.layers.item('name').findAllMasterPageItems();

Thank you so much! I created a test script that runs from the scripts panel. In this case, it really worked out.

main();

function main() {
    var doc = app.activeDocument;
    var layer, tf;
        try {
            layer = doc.layers.add({ name: 'erh_m_layer_x', layerColor: UIColors.GRAY });
        } catch (e) {
            layer = doc.layers.itemByName('erh_m_layer_x');
        }
    
        try {
            tf = doc.pages.lastItem().textFrames.add();
            tf.geometricBounds = [10,10,100,100];
            tf.name = 'TF_1';
        } catch (e) {
        }
    
    alert(doc.layers.itemByName('erh_m_layer_x').pageItems.everyItem().getElements()[0].name); //TF_1
    
    alert(doc.layers.itemByName('erh_m_layer_x').pageItems.length);
}

Now is my piece of code below. This is a long startup script,  the quoted part of it should process the content of the layer. This method is called when 4 text frames actually exist on the 'erh _m _layer' layer.

Alerts show 0 pageitems on 'm_layer'. The rest of the code works fine because... it doesn't use the layer collection.

Document.prototype.originVisibility = function() {
    var m_layer = app.activeDocument.layers.itemByName('erh_m_layer');
    
    //alert(m_layer.allPageItems.length); // 0! WHY???
    alert(m_layer.pageItems.length);   // 0! WHY???
    
    var l = app.activeDocument.masterSpreads.everyItem().pageItems.everyItem().getElements()
    .filter(function(pi){
        return pi.itemLayer == m_layer;
    })
    .forEach(function(pi){
        try {
            pi = resolve(pi.extractLabel('orig'));
            pi && pi.isValid && pi.visible = true;
        } catch(e) {
            tracelog('originVisibility: ***ERROR*** ' + e, $.line);
        }
    });
}

// In short, the code looks like this, the whole script is very large and many methods 
// are tied to class prototypes ...

var doc = app.activeDocument;
var tf = doc.pages.lastItem().textFrames.add(...);

var layer = doc.layers.add({ name: 'erh_m_layer', UIColors.RED });

// Now I create textframe duplicate and move it on the 'layer'
var tf_duplicate = tf.duplicate(tf.parentPage); // OK!
if (layer && layer.isValid) {
   tf_duplicate.itemLayer = layer; // OK! 
}


//Now I want to get  duplicate from Layer pageItems collection :

var ltf = doc.layers.itemByName('erh_m_layer').pageItems.everyItem().getElements()[0];
// this array is empty...

// also:  pageItems.count() == 0, allPageItems.length == 0


//Such code works:
var pItems = doc.pageItems.everyItem().getElements()
.filter(function(pi){ 
   return pi.itemLayer == layer;
});
//This array contains created textframe.