JavaScript quiz

Test your JavaScript knowledge with a free interactive quiz — 104 questions with answers and explanations. No signup needed to play.

What does `NaN` stand for in JavaScript?

1. What does `NaN` stand for in JavaScript?
2. What is the result of `0 ?? "fallback"`?
3. What is the output of `typeof function(){}`?
4. Which collects all remaining arguments into a true `Array` inside a function?
5. What does `typeof null` return in JavaScript?
6. What is the key difference between `??` and `||`?
7. What is hoisting in JavaScript?
8. What is a closure in JavaScript?
9. What does the `this` keyword refer to inside a regular function called in the global scope in non-strict mode?
10. What is the result of `"a" && "b"`?
11. Which of the following is NOT a falsy value in JavaScript?
12. What does `Object.keys()` return?

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