Chapter quiz · Plugins, Hooks & Lifecycle

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8 questions on Plugins, Hooks & Lifecycle. Pass 70% to clear the chapter.

Quiz

Plugins, Hooks & Lifecycle — Chapter Quiz

Eight questions on the plugin function signature, fastify-plugin, encapsulation, request and app hooks, decorators, and route prefixes.

0/ 9

Question 1
1
What is the signature of a Fastify plugin?
A(app, opts, done) => { ... } or async (app, opts) => { ... }B(req, res, next) => { ... }C(ctx) => { ... }Dclass Plugin extends Fastify { ... }
A plugin is a function that receives the (encapsulated) app instance and options. Async plugins resolve when done; callback plugins call done().
Question 2
2
Why wrap a plugin with fastify-plugin (fp)?
ATo make it run in parallel with other pluginsBTo expose its decorators and hooks to the parent scope (break encapsulation)CTo enable TypeScript typesDTo allow it to be async
By default each plugin is encapsulated — decorators and hooks stay inside. fp(...) opts out, so utilities like app.db are visible to everything that registers the plugin.
Question 3
3
A hook registered inside a plugin runs for routes in that plugin's scope only, unless fastify-plugin wraps it.
TTrueFFalse
Encapsulation applies to hooks too. Wrap the plugin with fp if you want the hook to run app-wide.
Question 4
4
Which hook runs **before** validation and the route handler, but **after** the request is parsed?
AonRequestBpreParsingCpreValidationDpreHandler
preValidation runs after body parsing and just before schema validation. preHandler runs after validation but before the handler itself.
Question 5
5
To run logic on the outgoing response, after the handler but before the bytes are sent, use the ____ hook.
onSend receives the payload and can mutate it (or replace it entirely) before Fastify writes to the socket. onResponse runs after the response is sent and can't change the payload.
Question 6
6
What does app.decorate('db', client) do?
AAdds db as a property on the app instance, accessible as app.dbBAdds db to every requestCReplaces an existing property if present, silentlyDAdds a route at /db
decorate attaches a value to the app. decorateRequest / decorateReply do the same for request and reply objects. Decorating a name twice throws.
Question 7
7
What URL does this route resolve to?
```
await app.register(async (app) => {
  app.get('/users', async () => []);
}, { prefix: '/api/v1' });
```
A/usersB/api/v1/usersC/v1/usersDIt throws — prefix is not a valid option
The prefix option prepends to every route inside the registered plugin, giving /api/v1/users.
Question 8
8
Which of these are request-lifecycle hooks in Fastify?
Select all that apply.
AonRequestBpreHandlerConResponseDonReadyEonClose
onRequest, preParsing, preValidation, preHandler, preSerialization, onSend, and onResponse are request-lifecycle hooks. onReady and onClose are app-lifecycle hooks.