In order to identify users across requests in an Express application, sessions can be used. By implementing sessions, each user will be assigned a unique session, allowing for the storage of user state.

To achieve this, we can use the express-session module, which is maintained by the Express team. To install this module, run the following command:

npm install express-session

Once installed, you can instantiate it in your application as follows:

const session = require('express-session')

As express-session is a middleware, it needs to be installed in Express using the following code:

const express = require('express')
const session = require('express-session')

const app = express()
app.use(session({
 'secret': '343ji43j4n3jn4jk3n'
}))

Here, ‘secret’ is the only required parameter, but there are additional options that can be used. It is recommended to use a randomly unique string as the value for the ‘secret’ parameter.

Once the configuration is set up, all requests to the app routes will now use sessions. The session object is attached to the request and can be accessed using req.session:

app.get('/', (req, res, next) => {
 // req.session
}

The req.session object can be used to retrieve and set data within the session. For example:

req.session.name = 'Flavio'
console.log(req.session.name) // 'Flavio'

Data stored in the session is serialized as JSON, allowing for the safe use of nested objects.

The location where session data is stored depends on the configuration of the express-session module. It can be stored in memory (not recommended for production), in a database like MySQL or MongoDB, or in a memory cache like Redis or Memcached.

Please refer to https://github.com/expressjs/session for a list of compatible caching stores provided by third-party packages.

In all cases, the session id is stored in a cookie on the client-side, and the data is stored server-side. The client sends the session id along with every HTTP request.

The default storage option is memory, which is suitable for development purposes but not recommended for production. For production environments, it is recommended to use a memory cache like Redis, which requires setting up its own infrastructure.

Another popular package for session management in Express is cookie-session. However, it stores data client-side in the cookie, which is not recommended due to limitations in size and security considerations.

Tags: Express sessions, user identification, session management, express-session, cookies, memory cache, Redis, cookie-session