callback-hell.js

router.post('/:id/title-image', (req, res, next) => {

    lwip.open(req.file.buffer, 'jpg', (err, image) => {
        if (err) { next(err); return; }
        let ratio = (image.width() > 960 ? (960 / image.width()) : 1);
        image.scale(ratio, (err, image) => {
            if (err) { next(err); return; }
            image.crop(image.width(), Math.min((image.width() / 2), image.height()), (err, image) => {
                if (err) { next(err); return; }
                image.toBuffer('jpg', { quality: 80 }, (err, buffer) => {
                    if (err) { next(err); return; }
                    db.doc.attachment.write(req.params['id'], "TITLE_IMAGE", buffer, "image/jpeg", (err) => {
                        if (err) { next(err); return; }
                        res.sendStatus(200);
                    });
                });
            });
        });
    });

});