thanks @Jarda , that’d be great for everyone!
until then you can use:
Array.from(app.activeDocument.layers)
which return a normal array of layers
or the following function I created to get ALL LAYERS regardless of “depth”
it accepts one argument : the root of layers
it could be doc’s layers or a group of layers
function flatLayers(lys) {
return lys.flatMap((v) => v.layers ? [v].concat(flatLayers(v.layers)) : v)
}
and use it like so:
flatLayers(app.activeDocument.layers)