How do you handle sessions in Koa.js?

Koa.js - Interview Questions

Handling sessions in Koa.js typically involves using middleware to manage and persist session data between HTTP requests. One popular middleware for session management in Koa.js is koa-session. This middleware simplifies the process of handling sessions and allows developers to store session data in various storage backends.

Here's a step-by-step guide on how you can handle sessions in Koa.js using the koa-session middleware:

1. Install koa-session : Begin by installing the koa-session middleware using npm or yarn.

npm install koa-session?

2. Use koa-session Middleware in Your Koa Application : Import and use the koa-session middleware in your Koa application. Make sure to set the app.keys property with an array of secret keys to enhance the security of session data.

const Koa = require('koa');
const session = require('koa-session');
const app = new Koa();

// Set the app.keys property with an array of secret keys
app.keys = ['key1', 'key2', 'key3'];

// Use the koa-session middleware for session management
app.use(session(app));

// Your route handlers go here

// Start the Koa application
const port = 3000;
app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});?

3. Accessing and Modifying Session Data : Once the koa-session middleware is applied, you can access and modify session data through the ctx.session object within your route handlers.

app.use(async (ctx, next) => {
  // Access and modify session data
  ctx.session.views = (ctx.session.views || 0) + 1;

  // Continue to the next middleware
  await next();
});

app.use(async (ctx) => {
  // Access session data in another middleware or route handler
  const views = ctx.session.views || 0;
  ctx.body = `Total views: ${views}`;
});?

In this example, the number of views is stored in the ctx.session.views property. The ctx.session object is automatically created and managed by the koa-session middleware.

4. Configuring Session Options : You can configure various options for the koa-session middleware, such as the session key, storage backend, and session expiration.

app.use(session({
  key: 'koa:sess', // Custom session key
  maxAge: 86400000, // Session expiration time (in milliseconds)
  rolling: true, // Renew session on every request
  renew: true, // Renew session even if it hasn't been modified
}));?

Customize these options based on your application's requirements.