Saves a file in Photoshop as jpg. File path is based on current document and filename is based on current layer.

Save as JPEG.jsx

var doc = app.activeDocument;
var fileName = doc.activeLayer.name;
var outputLocation= File( doc.path + "/" + fileName );

save( outputLocation );

function save( outputLocation ) {

    var saveOptions = new ExportOptionsSaveForWeb;

    saveOptions.format = SaveDocumentType.JPEG;
    saveOptions.optimized = true;
    saveOptions.interlaced = true;
    saveOptions.quality = 100;

    doc.exportDocument( new File( outputLocation ), ExportType.SAVEFORWEB, saveOptions );

}