💻 Computer Science & IT

JavaScript fundamentals

Closures, the event loop, equality, and the behaviour that still catches experienced developers out.

8questions

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Question 1 of 8

What does a closure capture?

Question 2 of 8

`typeof null` returns:

Question 3 of 8

Which comparison is true?

Question 4 of 8

In the event loop, a promise callback (microtask) runs:

Question 5 of 8

What is the difference between `let` and `var`?

Question 6 of 8

`[1, 2, 3].map(f)` returns:

Question 7 of 8

What does `async` before a function guarantee?

Question 8 of 8

Optional chaining `a?.b` evaluates to undefined when:

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