Now that you sort of have the idea of generators,
the next step is to make the simplest Koa app, ever.

Unlike Express where you use node.js’ req and res object,
Koa exposes its own very similar this.request and this.response objects.
Also unlike Express and node.js,
Koa uses getters and setters instead of methods.

For example,
in node.js, you might be used to the following:

  1. res.statusCode = 200;
  2. res.setHeader('Content-Type', 'text/plain');
  3. res.end('hello world');

In Express, there is a shortcut:

  1. res.send('hello world');

However, in Koa, we use getter/setter:

  1. app.use(function* () {
  2.   this.response.body = 'hello world';
  3. })

Exercise

Make an app that returns hello world for every response.
Verify the following are correct:

  • Status Code: 200
  • Content-Length: 11
  • Content-Type: text/plain; charset=utf-8

Hint: Koa sets these headers for you with strings!