Introduction to Koa Session

Koa-session is a powerful and easy-to-use middleware for managing sessions in Koa applications. It provides a straightforward API for working with user sessions, making it easier to build secure and scalable web applications. Below, we explore some of the most useful APIs available in koa-session, complete with code snippets to get you started.

Installing Koa-Session

  
    npm install koa-session
  

Using Koa-Session

First, you’ll need to initialize Koa-session in your Koa application. Here is a simple example of how to set it up:

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

    app.keys = ['some secret hurr'];

    app.use(session(app));

    app.use(ctx => {
      // count is initialized to 0 if not already set
      let n = ctx.session.views || 0;
      ctx.session.views = ++n;
      ctx.body = `${n} views`;
    });

    app.listen(3000);
  

Configuration Options

Koa-session comes with several configuration options that allow you to customize session behavior.

  
    const sessionConfig = {
      key: 'koa.sess', // cookie name
      maxAge: 86400000, // cookie expiry time in ms (1 day)
      autoCommit: true, // automatically commit headers
      overwrite: true, // can overwrite or not
      httpOnly: true, // cookie is HTTP only
      signed: true, // signature
      rolling: false, // reset maxAge on every response
      renew: false, // renew session when it is nearly expired
    };

    app.use(session(sessionConfig, app));
  

Working with Sessions

Setting Session Data

You can set session data by assigning values to the ctx.session object:

  
    app.use(ctx => {
      ctx.session.userId = '12345';
      ctx.body = 'Session set';
    });
  

Getting Session Data

Retrieve session data from the ctx.session object:

  
    app.use(ctx => {
      const userId = ctx.session.userId;
      ctx.body = `User ID: ${userId}`;
    });
  

Destroying a Session

You can destroy a session by setting ctx.session = null:

  
    app.use(ctx => {
      ctx.session = null;
      ctx.body = 'Session destroyed';
    });
  

Advanced Example

Here is a more advanced example that demonstrates how to use some of the koa-session features:

  
    const Koa = require('koa');
    const session = require('koa-session');
    const Router = require('@koa/router');

    const app = new Koa();
    const router = new Router();

    app.keys = ['super-secret-key'];

    const sessionConfig = {
      key: 'koa.sess',
      maxAge: 86400000,
      httpOnly: true,
      signed: true,
      rolling: true,
      renew: true,
    };

    app.use(session(sessionConfig, app));

    router.get('/login', ctx => {
      ctx.session.userInfo = { username: 'testUser' };
      ctx.body = 'Logged in!';
    });

    router.get('/profile', ctx => {
      if (ctx.session.userInfo) {
        ctx.body = `User: ${ctx.session.userInfo.username}`;
      } else {
        ctx.status = 401;
        ctx.body = 'Please log in first';
      }
    });

    router.get('/logout', ctx => {
      ctx.session = null;
      ctx.body = 'Logged out!';
    });

    app
      .use(router.routes())
      .use(router.allowedMethods());

    app.listen(3000, () => {
      console.log('Server running on http://localhost:3000');
    });
  

This advanced example sets up a login route that stores user information in the session, a profile route that checks if the user is logged in, and a logout route that destroys the session.

With these examples, you should have a good understanding of how to use koa-session to manage user sessions effectively in your Koa applications.

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