[Q] Is there way to check if the LayerSet is ArtBoard without selecting?

is this a riddle, why not add description what your linking.

I add here a translated version of @songgebs46585277  addition. Though the method used can be done better. saving a file then reopening it and then cropping makes the script slow. Better is making a duplicate of the current document, then crop to the active artboard and export this. This is faster.

An example of this is export layer comps file which comps with photoshop. I use this same approach in a script i got for export layer comps and artboards in a script of mine. Normally its either one or the other, you cant export layer comps from a file which has artboards. 

You function will not do anything since the last function is never called??

// Author: WangSongSong
// Source: https://github.com/songgeb/ExtendScript-Helper/blob/master/artboard.jsx

// Since the current (April 19, 2018) official api does not support the drawing board attribute query, 
// write a method to determine whether the layer is a drawing board.
function isArtboard (layer) {
    var itemIndex = layer.itemIndex;
    try {
        if (app.activeDocument.backgroundLayer) {
            itemIndex --;
        }
    } catch (e) {
    }

    var ref = new ActionReference();
    ref.putIndex(stringIDToTypeID("layer"), itemIndex);
    var desp = executeActionGet(ref);
    try {
        return desp.getBoolean(stringIDToTypeID("artboardEnabled"));
    } catch (e) {
        return false;
    }
}

// Get the size of the artboard and the coordinates of the origin from the upper left corner of the entire canvas
function getArtboardBounds (artboardLayer) {
    var originalRuler = app.preferences.rulerUnits;
    
    app.preferences.rulerUnits = Units.PIXELS;
    var itemIndex = artboardLayer.itemIndex;
    try {
        if (app.activeDocument.backgroundLayer) {
            itemIndex --;
        }
    } catch (e) {
    }
    var ref = new ActionReference();
    ref.putIndex(stringIDToTypeID("layer"), itemIndex);
    var desp = executeActionGet(ref);
    var theBounds = desp.getObjectValue(stringIDToTypeID('bounds'));
    var theX = theBounds.getInteger(stringIDToTypeID('left'));
    var theY = theBounds.getInteger(stringIDToTypeID('top'));
    var theX2 = theBounds.getInteger(stringIDToTypeID('right'));
    var theY2 = theBounds.getInteger(stringIDToTypeID('bottom'));
    
    app.preferences.rulerUnits = originalRuler;
    return [UnitValue(theX, "px"), UnitValue(theY, "px"), UnitValue(theX2, "px"), UnitValue(theY2, "px")];
}

// Export an artboard separately, similar to the function of "File -> Export -> Artboard to File" in ps
function exportArtboardAsPNG(artboard, exportDirPath) {
    // Create a new document and copy the artboard layer group to guoqu 
    var currentDoc = app.activeDocument;
    var newDoc = app.documents.add (currentDoc.width, currentDoc.height, currentDoc.resolution, null, NewDocumentMode.RGB, DocumentFill.TRANSPARENT);
    app.activeDocument = currentDoc;
    var newArtboard = artboard.duplicate (newDoc);
    app.activeDocument = newDoc;
    // Record the size of the artboard
    var bounds = getArtboardBounds(newArtboard);
    var tmpFilePath = exportDirPath + "/tmp.png";
    // Export a temporary picture that only contains the artboard, but the size is still the original size
    saveDocumentAsPNG(tmpFilePath);
    newDoc.close(SaveOptions.DONOTSAVECHANGES);
    // ps opens the temporary picture, crops the artboard area according to the size of the artboard, and exports the cropped part
    var tmpFile = new File(tmpFilePath);
    newDoc = app.open (tmpFile);
    newDoc.crop(bounds);
    saveDocumentAsPNG(exportDirPath+"/result.png");
    tmpFile.remove();
    newDoc.close(SaveOptions.DONOTSAVECHANGES);
}

c.pfaffenbichler​ Thank you very much for the pointer.