Quiz

JavaScript Async Quiz

8 questions about Promise, async/await, and how JavaScript handles operations that take time.

questions

~4 min

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Question 1 of 8

Why does JavaScript need asynchronous code at all?

So the code runs faster line by line✓✗ So long-running operations don't freeze the rest of the page✓✗ It's an outdated concept✓✗ Only for working with arrays✓✗

Question 2 of 8

How many states can a Promise have?

One✓✗ Two✓✗ Three: pending, fulfilled, rejected✓✗ Infinitely many✓✗

Question 3 of 8

What does the await keyword do?

Freezes the entire browser✓✗ Waits for a promise's result inside an async function, without blocking the rest of the code✓✗ Creates a new promise✓✗ Replaces a for loop✓✗

Question 4 of 8

Which kind of function needs to be marked in order to use await inside it?

function✓✗ async function✓✗ await function✓✗ Any regular function✓✗

Question 5 of 8

What's the difference between setTimeout and setInterval?

No difference✓✗ setTimeout runs once, setInterval repeats✓✗ setInterval runs once, setTimeout repeats✓✗ setTimeout only works with promises✓✗

Question 6 of 8

How do you handle an error in a promise?

With .catch() or try/catch with async/await✓✗ Errors in promises can't be handled✓✗ Only with console.log✓✗ With if/else✓✗

Question 7 of 8

What does an async function return if it has no explicit return?

undefined✓✗ A Promise that resolves to undefined✓✗ An error✓✗ null✓✗

Question 8 of 8

What is the event loop, in simple terms?

A for loop for events✓✗ A mechanism that watches a task queue and runs tasks once the main code is free✓✗ An outdated way of handling clicks✓✗ A function for working with arrays✓✗

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