Deleting layers with a special suffix

I modified the script I posted to help you now to do what you want to do Keep the Background and Layers with a _alpha layer name suffix.  Basically a one line function.  Name this script "KeepBGandAlpha.jsx"    I removed the code that was not needed and added one line.

if ( !layer.isBackgroundLayer & layer.name.indexOf("_alpha")==-1 ) layer.remove();

To complete the Script you need to add a Save see if you cans figure where that code needs to added and where you want to save and name the  file for the modified document. If you save over the current document's backing  file a programming error could destroy your documents.

/* ==========================================================
// 2017  John J. McAssey (JJMack) 
// ======================================================= */
// This script is supplied as is. It is provided as freeware. 
// The author accepts no liability for any problems arising from its use.
// enable double-clicking from Mac Finder or Windows Explorer
#target photoshop // this command only works in Photoshop CS2 and higher
// bring application forward for double-click events
app.bringToFront();
// ensure at least one document open
if (!documents.length) alert('There are no documents open.', 'No Document');
else {
	// declare Global variables
	var allLayers = ""; 
	//main(); // at least one document exists proceed
    app.activeDocument.suspendHistory('Some Process Name','main()');
}
///////////////////////////////////////////////////////////////////////////////
//                            main function                                  //
///////////////////////////////////////////////////////////////////////////////
function main() {
	// declare local variables
	var orig_ruler_units = app.preferences.rulerUnits;
	var orig_type_units = app.preferences.typeUnits;
	var orig_display_dialogs = app.displayDialogs;
	app.preferences.rulerUnits = Units.PIXELS;  	// Set the ruler units to PIXELS
	app.preferences.typeUnits = TypeUnits.POINTS;   // Set Type units to POINTS
	app.displayDialogs = DialogModes.NO;	    	// Set Dialogs off
	try { code(); }
	// display error message if something goes wrong
	catch(e) { alert(e + ': on line ' + e.line, 'Script Error', true); }
	app.displayDialogs = orig_display_dialogs;  	// Reset display dialogs 
	app.preferences.typeUnits  = orig_type_units;	// Reset ruler units to original settings 
	app.preferences.rulerUnits = orig_ruler_units;	// Reset units to original settings
}
///////////////////////////////////////////////////////////////////////////////
//                           main function end                               //
///////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////////////////////////////////////////////
// The real code is embedded into this function so that at any point it can return //
// to the main line function to let it restore users edit environment and end      //
/////////////////////////////////////////////////////////////////////////////////////
function code() {
	processArtLayers(activeDocument) 
}
function processArtLayers(obj) {  
    for( var i = obj.artLayers.length-1; 0 <= i; i--) {processLayers(obj.artLayers[i])}  
    for( var i = obj.layerSets.length-1; 0 <= i; i--) {processArtLayers(obj.layerSets[i])}  
} 
function processLayers(layer) { 
	if ( !layer.isBackgroundLayer & layer.name.indexOf("_alpha")==-1 ) layer.remove();
}

Try this, as long as your layer stacking pattern is as described it should work:

/*

https://community.adobe.com/t5/photoshop/deleting-layers-with-a-special-suffix/m-p/11772325
Deleting layers with a special suffix

I really wanted to select layers using a regular expression:

/^((?!_alpha|Background).)*$/igm

However, I ended up writing a script based on the very specific layer stacking order pattern, which is far from ideal:

flower
flower_filter
flower_alpha *
grass
grass_filter
grass_alpha *
sky
sky_filter
sky_alpha *
Background

I believe that it gets the job done, even if it is inflexible and not the thing of beauty that I was hoping for...

*/


#target photoshop

// Layer count divided by 3, less 1
var layersLength = app.activeDocument.layers.length - 1;
var repeatValue = layersLength / 3 - 1;
//alert(repeatValue);

// Deselect all layers
app.runMenuItem(stringIDToTypeID('selectNoLayers'));

// Tidy up the first set of 3 layers
selectFrontLayer(false);
addSelectBackwardLayer(false);
removeSelectedLayers();

// Tidy up any remaining layer triplets
for (i = 0; i < repeatValue; i++) {
    repeatSteps();
}

// Here be functions

function removeSelectedLayers() {
    var c2t = function (s) {
        return app.charIDToTypeID(s);
    };

    var s2t = function (s) {
        return app.stringIDToTypeID(s);
    };

    var descriptor = new ActionDescriptor();
    var list = new ActionList();
    var reference = new ActionReference();

    reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("targetEnum"));
    descriptor.putReference(c2t("null"), reference);
    list.putInteger(14);
    list.putInteger(15);
    descriptor.putList(s2t("layerID"), list);
    executeAction(s2t("delete"), descriptor, DialogModes.NO);
}

function selectFrontLayer(makeVisible) {
    var c2t = function (s) {
        return app.charIDToTypeID(s);
    };

    var s2t = function (s) {
        return app.stringIDToTypeID(s);
    };

    var descriptor = new ActionDescriptor();
    var list = new ActionList();
    var reference = new ActionReference();

    reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("front"));
    descriptor.putReference(c2t("null"), reference);
    descriptor.putBoolean(s2t("makeVisible"), makeVisible);
    list.putInteger(15);
    descriptor.putList(s2t("layerID"), list);
    executeAction(s2t("select"), descriptor, DialogModes.NO);
}

function addSelectBackwardLayer(makeVisible) {
    var c2t = function (s) {
        return app.charIDToTypeID(s);
    };

    var s2t = function (s) {
        return app.stringIDToTypeID(s);
    };

    var descriptor = new ActionDescriptor();
    var list = new ActionList();
    var reference = new ActionReference();

    reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("backwardEnum"));
    descriptor.putReference(c2t("null"), reference);
    descriptor.putEnumerated(s2t("selectionModifier"), s2t("selectionModifierType"), s2t("addToSelection"));
    descriptor.putBoolean(s2t("makeVisible"), makeVisible);
    list.putInteger(14);
    list.putInteger(15);
    descriptor.putList(s2t("layerID"), list);
    executeAction(s2t("select"), descriptor, DialogModes.NO);
}

function repeatSteps() {

    select(false);
    select2(false);
    delete2();

    function select(makeVisible) {
        var c2t = function (s) {
            return app.charIDToTypeID(s);
        };

        var s2t = function (s) {
            return app.stringIDToTypeID(s);
        };

        var descriptor = new ActionDescriptor();
        var list = new ActionList();
        var reference = new ActionReference();

        reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("backwardEnum"));
        descriptor.putReference(c2t("null"), reference);
        descriptor.putBoolean(s2t("makeVisible"), makeVisible);
        list.putInteger(12);
        descriptor.putList(s2t("layerID"), list);
        executeAction(s2t("select"), descriptor, DialogModes.NO);
    }

    function select2(makeVisible) {
        var c2t = function (s) {
            return app.charIDToTypeID(s);
        };

        var s2t = function (s) {
            return app.stringIDToTypeID(s);
        };

        var descriptor = new ActionDescriptor();
        var list = new ActionList();
        var reference = new ActionReference();

        reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("backwardEnum"));
        descriptor.putReference(c2t("null"), reference);
        descriptor.putEnumerated(s2t("selectionModifier"), s2t("selectionModifierType"), s2t("addToSelection"));
        descriptor.putBoolean(s2t("makeVisible"), makeVisible);
        list.putInteger(11);
        list.putInteger(12);
        descriptor.putList(s2t("layerID"), list);
        executeAction(s2t("select"), descriptor, DialogModes.NO);
    }

    function delete2() {
        var c2t = function (s) {
            return app.charIDToTypeID(s);
        };

        var s2t = function (s) {
            return app.stringIDToTypeID(s);
        };

        var descriptor = new ActionDescriptor();
        var list = new ActionList();
        var reference = new ActionReference();

        reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("targetEnum"));
        descriptor.putReference(c2t("null"), reference);
        list.putInteger(11);
        list.putInteger(12);
        descriptor.putList(s2t("layerID"), list);
        executeAction(s2t("delete"), descriptor, DialogModes.NO);
    }
}

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

I'm a beginner in scripting, this is rather advanced I'm afraid. I know what I want to do, however, after many hours of dead ends I have nothing. Looking forward to seeing how this will be handled!

Method 1

Click layer "-flower", hold shift and click on layer "-sky_filter" to make a continuous selection of those layers. Then Ctrl click on the layers with named "alpha" to deselect them.

You now have the layer selected you want to delete, so click on the trash can icon bottom right of layers palette.

Method 2

Change Kind to Name, then input _alpha

Click folder icon to put these in a group

Change Name back to Kind

Select all layers except the layer group and background then delete layers.

In a script you can get an array of the all the layers object. Them process the layers array delete layers that are not the background without a layer name the suffix _alpha. Only the bottom layer can be a background layer and there is a bit that indicated its a  Background Layer a document could have many layers with the name Background. Layer Names need not be unique.