Uploading the avatar photo to contacts

Let's start by creating the endpoint to upload avatar photos:

// routes.js
var controller = require('./controller');

//...
server.post('/api/contacts/:contactId/avatar', 
controller.uploadAvatar);

Express itself does not process files automatically; it needs a plug-in that transforms the raw request into a more user-friendly API. This plug-in is named multer; it processes multipart/form-data, saving the file into a temporary path or making a buffer object, and then provides a JSON object with metadata information:

// Avatar endpoints
var upload = multer();
server.post('/api/contacts/:contactId/avatar', upload.single('avatar'),
controller.uploadAvatar
);
server.use('/avatar', express.static(__dirname + '/avatar'));

With the default configuration, it will save all the uploaded files into the temporary path of your operating system, which is /tmp in Unix systems; multer will attach a files attribute in the req object, which we can inspect to retrieve information...