Callback hell example

current.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);
                    });
                });
            });
        });
    });

});

try1.js

function processTitleImage (file, callback) {
  
    if (!file) {
        callback(new Error("No file"));
        return;
    }
    let type = file.originalname.split('.').pop();
    
    lwip.open(file.buffer, type, (err, image) => {
        if (err) { callback(err); return; }
        
        let ratio = (image.width() > 960 ? (960 / image.width()) : 1);
        let width = image.width() * ratio;
        let height = image.height() * ratio;
        
        async.series({
            scale: image.scale.bind(image, ratio),
            crop: image.crop.bind(image, width, Math.min((width / 2), height)),
            buffer: image.toBuffer.bind(image, 'jpg', { quality: 80 })
        }, callback);
    });
    
}

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

    processTitleImage(req.file, (err, result) => {
        if (err) { next(err); return; }
        db.doc.attachment.write(req.params['id'], "TITLE_IMAGE", result.buffer, "image/jpeg", (err) => {
            if (err) { next(err); return; }
            res.sendStatus(200);
        });
    });
  
});

try2.js

function processTitleImage (file, callback) {
  
    if (!file) {
        callback(new Error("No file"));
        return;
    }
    let type = file.originalname.split('.').pop();
    
    lwip.open(file.buffer, type, (err, image) => {
        if (err) { callback(err); return; }
        
        let ratio = (image.width() > 960 ? (960 / image.width()) : 1);
        let width = image.width() * ratio;
        let height = image.height() * ratio;
        
        image.batch()
            .scale(ratio)
            .crop(width, Math.min((width / 2), height))
            .toBuffer('jpg', { quality: 80 }, callback);
    });
  
}

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

    processTitleImage(req.file, (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);
        });
    });
  
});