fileObj = new File(filePath + layerName + ".psd");
    psdOpt = new PhotoshopSaveOptions();
    psdOpt.alphaChannels = true;
    psdOpt.annotations = true;
    psdOpt.embedColorProfile = false;
    psdOpt.layers = false;
    psdOpt.spotColors = false;
    activeDocument.saveAs(fileObj, psdOpt, true, Extension.LOWERCASE);

function exportPsdAM(fileName) {
    var desc = new ActionDescriptor();
    var desc2 = new ActionDescriptor();
    desc2.putBoolean( sTID( "maximizeCompatibility" ), true );
    desc.putObject( cTID( "As  " ), cTID( "Pht3" ), desc2 );
    desc.putPath( cTID( "In  " ), new File(fileName) );
    desc.putInteger( cTID( "DocI" ), 39 );
    desc.putBoolean( cTID( "Cpy " ), false );
    desc.putBoolean( cTID( "Lyrs" ), false );
    desc.putEnumerated( sTID( "saveStage" ), sTID( "saveStageType" ), sTID( "saveSucceeded" ) );
    executeAction( cTID( "save" ), desc, DialogModes.NO );
};
 
function cTID(s) {return app.charIDToTypeID(s);}
function sTID(s) {return app.stringIDToTypeID(s);}