Introduction to Koa Session and API Examples

koa-session is a middleware for managing sessions in Koa applications, one of the most popular Node.js frameworks. Understanding how to use koa-session effectively can significantly enhance the performance and security of your application.

Setting Up koa-session

To start using koa-session, you need to install the library:

npm install koa-session

Then you can set it up in your Koa application:

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

app.keys = ['your-session-secret'];
app.use(session(app));

app.use(ctx => {
  if (ctx.path === '/set') {
    ctx.session.user = 'john doe';
    ctx.body = 'session set';
  } else if (ctx.path === '/get') {
    ctx.body = ctx.session.user;
  }
});

app.listen(3000);

API Examples

Setting a Session Key

Use the below code to set a session key:

app.use(ctx => {
  ctx.session.key = 'value';
});

Getting a Session Key

You can retrieve a session key as follows:

app.use(ctx => {
  const key = ctx.session.key;
  ctx.body = key;
});

Session Expiry

Set an expiry time for a session:

app.use(session({
  key: 'koa.sess',
  maxAge: 86400000,
}, app));

Session Destroy

To destroy a session, use:

app.use(ctx => {
  ctx.session = null;
});

Renewing Sessions

To renew an existing session:

app.use(ctx => {
  ctx.sessionHandler.regenerateId();
});

Storing Data in Session

Multiple pieces of data can be stored in a session:

app.use(ctx => {
  ctx.session.user = {
    name: 'John Doe',
    age: 30,
  };
});

Full Application Example

Below is an example Koa application demonstrating various session functionalities introduced above:

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

app.keys = ['your-session-secret'];
app.use(session({
  key: 'koa.sess',
  maxAge: 86400000,
}, app));

app.use(ctx => {
  if (ctx.path === '/set') {
    ctx.session.user = { name: 'john doe', age: 30 };
    ctx.body = 'session set';
  } else if (ctx.path === '/get') {
    ctx.body = ctx.session.user;
  } else if (ctx.path === '/destroy') {
    ctx.session = null;
    ctx.body = 'session destroyed';
  } else if (ctx.path === '/renew') {
    ctx.sessionHandler.regenerateId();
    ctx.body = 'session renewed';
  }
});

app.listen(3000);
console.log('Server running on http://localhost:3000');

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Using koa-session effectively can enhance both performance and security, making it a vital component of any Koa.js application. Make sure to refer to the official documentation for a deeper dive into its numerous possibilities.

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