Try-catch for synchronous errors in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Node.js code with try-catch?

Consider this code snippet that uses try-catch to handle synchronous errors. What will it print to the console?

Node.js

try {
  JSON.parse('invalid json');
  console.log('Parsed successfully');
} catch (error) {
  console.log('Caught error:', error.message);
}

A Caught error: Unexpected token i in JSON at position 0

B Parsed successfully

C Caught error: SyntaxError

D No output, program crashes

💡 Hint

Think about what happens when JSON.parse receives invalid input.

JSON.parse throws a SyntaxError when given invalid JSON. The try-catch catches this error and logs its message.

❓ component_behavior

intermediate

How does try-catch behave with synchronous errors in Node.js?

Which statement best describes how try-catch handles synchronous errors in Node.js?

A It catches both synchronous and asynchronous errors automatically.

B It only catches synchronous errors thrown inside the try block.

C It cannot catch any errors in Node.js.

D It catches errors only if they are thrown asynchronously.

💡 Hint

Remember how asynchronous errors are handled differently in Node.js.

Try-catch blocks catch errors thrown synchronously inside the try block. Asynchronous errors require other handling methods.

🔧 Debug

advanced

Identify the error in this try-catch usage

What error will this Node.js code produce when run?

Node.js

try {
  setTimeout(() => {
    throw new Error('Async error');
  }, 100);
} catch (e) {
  console.log('Caught:', e.message);
}

A Caught: Async error

B SyntaxError: Unexpected token

C No output, program crashes with uncaught error

D Caught: undefined

💡 Hint

Think about how try-catch works with asynchronous callbacks.

The error is thrown asynchronously inside setTimeout, outside the try block's synchronous execution, so it is uncaught and crashes the program.

📝 Syntax

advanced

Which option shows correct try-catch syntax in Node.js?

Select the option that uses valid try-catch syntax to handle synchronous errors.

A

try {
  doSomething();
} catch {
  console.log(error);
}

B

try {
  doSomething();
} catch error {
  console.log(error);
}

C

try {
  doSomething();
} catch (error) {
  console.log(error.message
}

D

try {
  doSomething();
} catch (error) {
  console.log(error);
}

💡 Hint

Check the parentheses and braces around catch and error variable.

Option D uses correct syntax: catch keyword followed by parentheses with error variable, then braces for block.

❓ state_output

expert

What is the value of variable 'result' after this try-catch block?

Analyze the following code and determine the final value of 'result'.

Node.js

let result = '';
try {
  result += 'start-';
  throw new Error('fail');
  result += 'end-';
} catch (e) {
  result += 'caught-';
} finally {
  result += 'finally';
}

A "start-caught-finally"

B "start-end-caught-finally"

C "caught-finally"

D "start-finally"

💡 Hint

Remember that code after throw inside try is skipped, but finally always runs.

The throw stops execution inside try after 'start-'. Catch adds 'caught-'. Finally adds 'finally'. So result is 'start-caught-finally'.