Improving javaScript performance

I updated my script "Delete all empty layers faster" here Magic scripts for Photoshop

It uses AM code a lot instead DOM and I am not using recursion. It has progressbar and you can cancel script if you see it. But if script duration is under ~10s you don't see it. And I don't see progressbar even if document has 2000 layers.

I am using something like custom layers model with needed properties.

If you go in PS menu in: File > Scripts > Delete All Empty Layer ...you can compare it with script from Adobe. It uses DOM and recursion. Try document with 500 layers and higher.

I did some measurement and my script is 40-50× faster :-)

Anyway I am interested if I can be more specific in reference. I would like to specify property in property which I want.

Not using Photoshop DOM is very good idea.

I have good experience with:

1) Use references properly. Sometimes you don't need use targetEnum. So you don't need set active layer and then restore selected layer. You can save 20-40ms per layer. I changed my method from selecting layers and then deleting them at once. Now I am deleting layer without selecting them. Deleting without selection si faster then selection itself. In case of 1000 layers I improved script duration from 213 seconds to 121 seconds.

2) Sometimes you can put list references to layers into action reference if you want do same task with multiple layers. This should be fastest possible task with multiple layers.

function hideMulti(list){ 
    var idHd = charIDToTypeID( "Hd  " );
        var desc19 = new ActionDescriptor();
        var idnull = charIDToTypeID( "null" );
            var list9 = new ActionList();
            for(var i = 0, len = list.length; i < len; i++){
                var ref = new ActionReference();
                //some alternatives
                //layerRef.putIdentifier( cTID('Lyr '), list );
                //layerRef.putName( charIDToTypeID( "Lyr " ), "Layer 7" );
                ref.putIndex( charIDToTypeID('Lyr '), list );
                list9.putReference( ref );
            }
        desc19.putList( idnull, list9 );
    executeAction( idHd, desc19, DialogModes.NO );
}

3) Photoshop UI is usually frozen while script runing. You can force UI redraw.

4) If you want move/transform text layer, you don't need use classic transformation. With executeActionGet you can get textKey and change some properties inside. Like textClickPoint and then you put modified descriptor inside executeAction. With modifing textClickPoint you can move text layer without selecting it. You also can set 2D transformation matrix inside text layer (rotate/skew/scale)

5) Since CC2015 you can use built-in progressbar function. Show text messages about progress inside this dialog and have possibility to cancel anytime. If you update progressbar it takes a little time. So don't update progressbar too fast.

6) If you want read properties about layers you can be more specific in reference. Example:

$.hiresTimer;
var ref = new ActionReference(); 
ref.putProperty(charIDToTypeID( "Prpr" ), stringIDToTypeID("height"));
ref.putEnumerated( charIDToTypeID("Dcmn"), charIDToTypeID("Ordn"), charIDToTypeID("Trgt") );  
var desc = executeActionGet(ref); 
var height = desc.getDouble(stringIDToTypeID ("height"))    
alert("Property defined in reference.\nDocument height:"+height+"\nDuration: " + $.hiresTimer + "μs");
$.hiresTimer;
var ref = new ActionReference(); 
ref.putEnumerated( charIDToTypeID("Dcmn"), charIDToTypeID("Ordn"), charIDToTypeID("Trgt") );  
var desc = executeActionGet(ref); 
var height = desc.getDouble(stringIDToTypeID ("height"))    
alert("Property NOT defined in reference.\nDocument height:"+height+"\nDuration: " + $.hiresTimer + "μs");

On my PC I can get document height in 0,13ms if I define property in reference. Or in 168ms if I don't.

This is similar with layers.

7) try reduce the number of steps. Photoshop should do only necessarily things.

8) avoid DOM recursion

9) store stringID/charID in constants if you use this conversion very offten