Performance monitoring basics in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Express module.

Express

const express = require('[1]');

Drag options to blanks, or click blank then click option'

Ahttp

Bpath

Cfs

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'http' instead of 'express' will import the Node.js HTTP module, not Express.

Using 'fs' or 'path' imports file system or path modules, unrelated to Express.

The Express module is imported using require('express'). This allows you to create an Express app.

2fill in blank

medium

Complete the code to create a new Express application instance.

Express

const app = [1]();

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Ahttp

Bexpress

Crouter

Dserver

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'http' or 'server' will cause errors because they are not functions here.

Using 'router' is for routing, not creating the app instance.

Calling express() creates a new Express app instance to handle requests.

3fill in blank

hard

Fix the error in the code to log the response time using middleware.

Express

app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    console.log(`Response time: ${Date.now() - [1]ms`);
  });
  next();
});

Drag options to blanks, or click blank then click option'

AstartTime

Bres.start

Cstart

Dreq.start

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined variables like 'startTime' causes errors.

Using properties on req or res that don't exist will not work.

The variable start holds the start time. Subtracting it from the current time gives the response duration.

4fill in blank

hard

Fill both blanks to create a middleware that measures and logs request duration in milliseconds.

Express

app.use((req, res, next) => {
  const [1] = Date.now();
  res.on('[2]', () => {
    console.log(`Request took ${Date.now() - start}ms`);
  });
  next();
});

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Astart

Bbegin

Cfinish

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'begin' instead of 'start' for the variable name is uncommon and may confuse.

Listening to 'close' event instead of 'finish' may not always indicate response completion.

The variable start stores the start time. The event 'finish' fires when the response is done, so logging then shows total request time.

5fill in blank

hard

Fill all three blanks to create a simple route that responds with 'OK' and logs the request method and URL.

Express

app.[1]('/status', (req, res) => {
  console.log(`[2] request to [3]`);
  res.send('OK');
});

Drag options to blanks, or click blank then click option'

Aget

BPOST

Creq.url

Dreq.method

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase 'POST' in the method call causes errors; it should be lowercase 'get'.

Swapping req.method and req.url in the log message changes meaning.

The route uses get to handle GET requests. req.method gives the HTTP method, and req.url gives the requested URL.