Error Handling in Express Quiz

To pass the quiz, you must correctly answer at least 18 of the 20 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- What does the HTTP status code 201 mean? #### --distractors-- The request succeeded with no response body. --- The client is not authorized to access the resource. --- The requested resource does not exist. #### --answer-- A new resource was successfully created. ### --question-- #### --text-- Which status code indicates that the request succeeded but there is no response body? #### --distractors-- `200` --- `201` --- `301` #### --answer-- `204` ### --question-- #### --text-- What does the `304 Not Modified` status code tell the client? #### --distractors-- The resource has moved to a new permanent URL. --- The server is temporarily unavailable for maintenance. --- Authentication is required to access the resource. #### --answer-- Nothing has changed, so the client can use its cached version. ### --question-- #### --text-- What is the difference between status codes `401` and `403`? #### --distractors-- `401` means the resource is not found while `403` means the server is down. --- `401` means the request was malformed while `403` means the resource moved. --- `401` means the server crashed while `403` means the request timed out. #### --answer-- `401` means authentication is required while `403` means authenticated but does not have permission. ### --question-- #### --text-- Which status code means the server is temporarily overloaded or down for maintenance? #### --distractors-- `500` --- `502` --- `301` #### --answer-- `503` ### --question-- #### --text-- What does `res.status(200).json({ message: "Success" })` do in Express? #### --distractors-- Sends a `200` response with a plain text message. --- Sends a `200` response with no body. --- Redirects the client to the success page. #### --answer-- Sends a `200` response with a JSON body. ### --question-- #### --text-- What makes Express recognize a middleware function as an error handler? #### --distractors-- It is placed at the top of the middleware stack. --- It uses `res.error()` instead of `res.send()`. --- It is defined inside a route handler. #### --answer-- It has the parameters `err`, `req`, `res`, and `next`. ### --question-- #### --text-- Where should error-handling middleware be placed in an Express app? #### --distractors-- Before all route definitions. --- At the very top of the file, before any imports. --- Inside the first route handler that might throw an error. #### --answer-- At the end of the middleware stack, after all routes. ### --question-- #### --text-- In Express 4, what must you do to handle async errors in a route handler? #### --distractors-- Throw the error directly from the route handler and let Node.js handle it at the process level. --- Return the error object as a JSON response body with a 500 status code. --- Use `process.on('uncaughtException')` to catch all unhandled async errors globally. #### --answer-- Wrap async logic in `try/catch` and call `next(err)` to forward the error to the error handler. ### --question-- #### --text-- What is the purpose of an `asyncHandler` wrapper function in Express 4? #### --distractors-- It converts synchronous route handlers into asynchronous ones automatically. --- It automatically restarts the server and clears state when an error occurs. --- It replaces the error-handling middleware placed at the end of the middleware stack. #### --answer-- It avoids repeating `try/catch` in every route by forwarding rejected promises to `next`. ### --question-- #### --text-- How does Express 5 handle async errors differently from Express 4? #### --distractors-- Express 5 requires adding a global `process.on('unhandledRejection')` listener to catch async errors. --- Express 5 silently ignores async errors and only logs them to the console without stopping the app. --- Express 5 requires every async route to define its own dedicated error-handling middleware function. #### --answer-- Express 5 automatically forwards async errors and rejected promises to the error handler without needing `next(err)`. ### --question-- #### --text-- Where should a `404` catch-all middleware be placed in an Express app? #### --distractors-- Before all other routes, at the top of the file. --- Inside the error-handling middleware, as a fallback check. --- At the very end, after the error-handling middleware. #### --answer-- After all routes but before the error-handling middleware. ### --question-- #### --text-- Which of the following is a best practice for error handling in production Express apps? #### --distractors-- Always send the full stack trace to the client for easier debugging. --- Place error-handling middleware before your routes for faster processing. --- Handle all errors, including 404s, inside a single middleware function. #### --answer-- Log error details internally and return a user-friendly message instead of sending stack traces to users. ### --question-- #### --text-- How do you enable all of Express built-in debug messages when starting your app? #### --distractors-- Pass `{ debug: true }` to the `express()` constructor. --- Call `app.enable('debug')` before defining routes. --- Add `require('express-debug')` at the top of your entry file. #### --answer-- Set the `DEBUG` environment variable to `express:*` when running the app. ### --question-- #### --text-- What does `DEBUG=express:router node index.js` do? #### --distractors-- Enables all Express debug output, including middleware, routing, and application-level events. --- Disables all debug output entirely and runs the app in silent production mode. --- Logs only incoming HTTP request details like method and URL to the terminal. #### --answer-- Shows only router-related debug output, filtering out other Express namespaces. ### --question-- #### --text-- What is `morgan` used for in an Express application? #### --distractors-- Automatically catching and forwarding async errors in Express route handlers to `next`. --- Serving static files from a specified directory without defining individual routes. --- Connecting Express to a relational database and logging all executed queries. #### --answer-- Logging HTTP requests with details like method, URL, status code, and response time. ### --question-- #### --text-- What is the purpose of a health check route in an Express app? #### --distractors-- To automatically restart the server and reroute traffic when incoming request volume is too high. --- To record and forward all incoming HTTP requests to an external monitoring or analytics service. --- To inspect and block requests from IP addresses that are not on an approved allow-list. #### --answer-- To report whether the app is running correctly so load balancers and orchestrators can decide if the service is healthy. ### --question-- #### --text-- What does the `SIGTERM` signal tell a Node.js process to do? #### --distractors-- Restart immediately, clear all in-memory state, and re-initialize all active connections. --- Dump a full memory snapshot to disk for later analysis and debugging purposes. --- Force-kill all active database connections and close all open file descriptors right away. #### --answer-- Begin shutting down, giving the app a chance to finish existing work before exiting. ### --question-- #### --text-- What does calling `server.close()` do during a graceful shutdown? #### --distractors-- Immediately terminates all active connections and exits the process. --- Sends a 500 response to any clients currently connected. --- Deletes all in-memory session data and restarts the server. #### --answer-- Stops accepting new connections while allowing existing ones to finish. ### --question-- #### --text-- Why would you return a 503 status from your health check route during a graceful shutdown? #### --distractors-- To log the shutdown event and timestamp to an external monitoring dashboard for audit purposes. --- To force the orchestrator to immediately spin up a new replacement instance before shutdown completes. --- To notify all currently connected clients that their active sessions have been saved successfully. #### --answer-- To signal to the load balancer that the app is unavailable so it stops routing new traffic to it.