How to find out the grayscale percentage?

Through Scripting i can find out the color characteristics like cmyk and rgb percentages. But i could not know how to get the color characteristics of gray scale percentages. Kindly advice me.

Thanks

You really should have started a new topic but maybe this will work. It's modified from an export to PNG script posted last year.

/**
* @author Niels Bosma (niels.bosma@motorola.com
*/

var folder = Folder.selectDialog();
var document = app.activeDocument;
if(document && folder)
{   
    var exportOptions = new ExportOptionsJPEG();
    var type = ExportType.JPEG;
    // Setting ExportOptionsJPEG properties.
    exportOptions.antiAliasing = false;
    exportOptions.qualitySetting = 100;
    //exportOptions.artBoardClipping = true;
   
    var n = document.layers.length;
    for(var i=0; i<n; ++i)
    {
        hideAllLayers();
        var layer = document.layers;
        layer.visible = true;
   
        var file = new File(folder.fsName+"/"+layer.name+".jpg");
        document.exportFile(file, type, exportOptions);   
    }
   
    showAllLayers();
}

function hideAllLayers()
{
    forEach(document.layers, function(layer) {
        layer.visible = false;
    });
}

function showAllLayers()
{
    forEach(document.layers, function(layer) {
        layer.visible = true;
    });       
}

function forEach(collection, fn)
{
    var n = collection.length;
    for(var i=0; i<n; ++i)
    {
        fn(collection);
    }
}

//Cut and paste into any text editor and save as .jsx. Put into the AI Scripts preset folder and run. It requires an open document and will ask where to save the files.