GET route handling in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when accessing the GET route?

Consider this Express GET route handler:

app.get('/hello', (req, res) => {
  res.send('Hello World!');
});

What will the client receive when requesting /hello?

Express

app.get('/hello', (req, res) => {
  res.send('Hello World!');
});

A The client receives an empty response with status 200.

B The client receives a JSON object { message: 'Hello World!' }.

C The client receives a 404 Not Found error.

D The client receives the text 'Hello World!' as the response body.

💡 Hint

Look at what res.send does with a string argument.

The res.send method sends the string as the response body with status 200 by default.

📝 Syntax

intermediate

Which option correctly defines a GET route with a URL parameter?

Which of the following Express GET route definitions correctly captures a URL parameter named id?

A app.get('/user/id', (req, res) => { res.send(req.params.id); });

B app.get('/user/:id', (req, res) => { res.send(req.params.id); });

C app.get('/user/<id>', (req, res) => { res.send(req.params.id); });

D app.get('/user/:id?', (req, res) => { res.send(req.params.id); });

💡 Hint

URL parameters use a colon : before the name.

Option B uses /:id which correctly defines a required URL parameter named id.

Option B treats 'id' as a literal path segment, not a parameter.

Option B uses invalid syntax with angle brackets.

Option B defines an optional parameter with ?, which is valid but changes the route behavior.

🔧 Debug

advanced

Why does this GET route handler cause an error?

Examine this Express GET route handler:

app.get('/data', (req, res) => {
  const data = fetchData();
  res.send(data);
});

Assuming fetchData is an async function returning a Promise, why does this code cause an error or unexpected behavior?

Express

app.get('/data', (req, res) => {
  const data = fetchData();
  res.send(data);
});

A Because res.send cannot be called inside a GET route handler.

B Because fetchData is not defined, causing a ReferenceError.

C Because fetchData returns a Promise, res.send sends the Promise object instead of the resolved data.

D Because the route path '/data' is invalid syntax.

💡 Hint

Think about what happens when you call an async function without awaiting it.

Since fetchData returns a Promise, calling it without await means data is a Promise object. Sending this Promise directly sends the object, not the resolved value.

❓ state_output

advanced

What is the response when accessing this GET route multiple times?

Consider this Express code:

let count = 0;
app.get('/count', (req, res) => {
  count += 1;
  res.send(`Count is ${count}`);
});

What will the client see when requesting /count three times in a row?

Express

let count = 0;
app.get('/count', (req, res) => {
  count += 1;
  res.send(`Count is ${count}`);
});

A The client sees 'Count is 1', then 'Count is 2', then 'Count is 3' on each request.

B The client sees 'Count is undefined' because count is not initialized.

C The client sees 'Count is 0' on the first request and errors on the next.

D The client always sees 'Count is 1' on every request.

💡 Hint

Think about how the variable count changes with each request.

The variable count is stored in the server's memory and increments by 1 on each request, so the response reflects the updated count.

🧠 Conceptual

expert

Which statement about Express GET route matching is true?

Given these routes:

app.get('/item/new', handler2);
app.get('/item/:id', handler1);

Which statement correctly describes how Express matches requests?

A A request to '/item/new' matches handler2 because exact routes have priority over parameter routes.

B A request to '/item/new' matches handler1 because parameter routes match before exact routes.

C A request to '/item/123' matches handler2 because it is defined second.

D A request to '/item/new' causes an error because routes conflict.

💡 Hint

Think about route specificity and matching order in Express.

Express matches routes in order and prefers exact string matches over parameter matches when both could match the same path.