Chapter quiz · Koa Foundations

Test what you learned.

8 questions on Koa Foundations. Pass 70% to clear the chapter.

Quiz

Koa Foundations — Chapter Quiz

Eight questions on ctx, app.use, ctx.body, request/response aliases, cascading basics, async middleware, app.callback, and app.keys.

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Question 1
1
What does Koa store on ctx that Express does not provide out of the box?
AA merged ctx.body / ctx.status response API alongside request helpersBA built-in routerCA database connection poolDA template engine
Koa's context (ctx) bundles both the Node req/res objects and a clean response API (ctx.body, ctx.status, ctx.set) in one object. Express exposes req and res separately.
Question 2
2
Which one-liner sets a plain-text response body in Koa?
Ares.send(\"hello\")Bctx.body = \"hello\"Cctx.send(\"hello\")Dctx.write(\"hello\")
Assigning to ctx.body is the idiomatic Koa response. Koa automatically infers Content-Type and Content-Length from the assigned value.
Question 3
3
What is ctx.request.url an alias for inside Koa's context?
Actx.urlBctx.pathCctx.hrefDctx.origin
Koa delegates many ctx.request.* properties directly onto ctx. So ctx.url, ctx.method, ctx.headers, etc. are shortcuts for ctx.request.url, ctx.request.method, etc.
Question 4
4
What does app.callback() return?
AThe Koa application instanceBA Node http.RequestListener suitable for http.createServerCA Promise that resolves when the server startsDThe middleware stack array
app.callback() returns a (req, res) => void callback compatible with http.createServer. app.listen() calls it internally, but app.callback() lets you pass Koa into https.createServer or a test helper.
Question 5
5
Why must Koa middleware functions be async (or return a Promise) when they call await next()?
AKoa uses setImmediate internally and needs a callbackBSo Koa can await the entire downstream chain before running post-next() logicCNode.js requires all HTTP handlers to be asyncDExpress compatibility
Koa's cascade is Promise-based. When you await next(), Koa awaits the whole downstream stack. Code written after await next() runs on the way back up — impossible with plain callbacks.
Question 6
6
app.use() accepts only one middleware function per call in Koa 2.
TTrueFFalse
Unlike some frameworks, app.use() in Koa 2 takes a single middleware function. Pass multiple middlewares by chaining multiple app.use() calls or composing with koa-compose.
Question 7
7
Set app.___ to an array of secret strings so Koa can sign cookies with ctx.cookies.set('name', 'val', { signed: true }).
app.keys is a Keygrip-compatible array of secrets used to HMAC-sign cookie values. Koa rotates to the next key automatically when the first is revoked.
Question 8
8
Which of the following are valid ways to start a Koa HTTP server?
Select all that apply.
Aapp.listen(3000)Bhttp.createServer(app.callback()).listen(3000)Capp.start(3000)Dhttps.createServer(tlsOptions, app.callback()).listen(443)
app.listen() is a shortcut for the http.createServer form. app.callback() lets you plug Koa into any Node server (HTTP, HTTPS, HTTP/2). app.start() does not exist.