JavaScript quiz

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

What is the value of `b` after `const a = {x: 1}; const b = {...a, y: 2};`?

1. What is the value of `b` after `const a = {x: 1}; const b = {...a, y: 2};`?
2. What does `"hello world".includes("world")` return?
3. How do you import a default export from `./math.js`?
4. What does `user?.profile?.name` evaluate to if `user.profile` is `null`?
5. Which method converts a JSON string into a JavaScript object?
6. What does the `this` keyword refer to inside a regular function called in the global scope in non-strict mode?
7. What does spread do in a function call: `Math.max(...[1, 2, 3])`?
8. Which keyword is used to declare a block-scoped variable in modern JavaScript?
9. What does this print? ```js const obj = {a: 1}; obj.a = 2; console.log(obj.a); ```
10. What is the value of `third` after `const [, , third] = [10, 20, 30];`?
11. What does `extends` do in a class declaration?
12. How do you declare an arrow function?

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