JPEG var options.... how do I get them?

Question

CS4-AI  Mac
I'd like to change the "SaveLayersPNG200dpi.jsx" to export to JPEG. How do I get a list of the export options for jpgs? I looked in the scripting pdf's but I couldn't find it.
Below is the script, I assume ( I don't know anything about scripting.. actually I know very little about most things : ) that I can replace the "var options" and the document type for JPEG?
thanks!  j
var folder = Folder.selectDialog();
var document = app.activeDocument;
if(document && folder)
var options = new ExportOptionsPNG24();
options.antiAliasing = true;
options.transparency = false;
options.artBoardClipping = true;
options.verticalScale = 138.889;
options.horizontalScale = 138.889;
var n = document.layers.length;
for(var i=0; i<n; ++i)
hideAllLayers();
var layer = document.layers[i];
layer.visible = true;
var file = new File(folder.fsName+"/"+layer.name+".png");
document.exportFile(file,ExportType.PNG24,options);
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[i]);

Answer 1

at this point it will export layers that are locked and/or invisible, I'll need to do some research. It would be nice to incorporate this into the script so that it becomes more similar to choosing selected layer comps in PS.
thanks for the link to the resources,
best regards,
j