Return how many layers are there in document — Photoshop script

getLayersCount.jsx

function getLayersCount() {
    var ref = new ActionReference();
    ref.putProperty (stringIDToTypeID ("property"), charIDToTypeID('NmbL'))
    ref.putEnumerated(charIDToTypeID('Dcmn'), charIDToTypeID('Ordn'), charIDToTypeID('Trgt'));
    var count = executeActionGet(ref).getInteger(charIDToTypeID('NmbL'));
    return count
}