var filePath;
if($.os.search(/windows/i)!=-1) {
	//for Win
	filePath = "C:\\layercomps\\";
} else {
	//for Mac
	filePath = "~/layercomps/";
}
var exp = new ExportOptionsSaveForWeb();
exp.format = SaveDocumentType.JPEG;
exp.quality = 70;
var doc = activeDocument;

for(var i=0; i<doc.layerComps.length;i++) {
	var imgFile = new File(filePath + doc.layerComps[i].name + ".jpg");
	doc.layerComps[i].apply();
	doc.exportDocument(imgFile, ExportType.SAVEFORWEB, exp);
}