app.js

/**
 * A very simple flash example.
 * Only uses JSON for simplicity.
 */

const rawBody = require('raw-body');
const session = require('koa-session');
const Koa = require('koa');
const app = module.exports = new Koa();

// required for signed cookie sessions
app.keys = ['key1', 'key2'];
app.use(session(app));

app.use(async (ctx, next) => {
  if (ctx.method !== 'GET' || ctx.path !== '/messages') return await next();

  // get any messages saved in the session
  const messages = ctx.session.messages || [];
  ctx.body = messages;

  // delete the messages as they've been deliverd
  delete ctx.session.messages;
});

app.use(async (ctx, next) => {
  if (ctx.method !== 'POST' || ctx.path !== '/messages') return await next();

  // the request string is the flash message
  const message = await rawBody(ctx.req, {
    encoding: 'utf8'
  });

  // push the message to the session
  ctx.session.messages = ctx.session.messages || [];
  ctx.session.messages.push(message);

  // tell the client everything went okay
  ctx.status = 204;
});

if (!module.parent) app.listen(3000);