JavaScript Quiz

Pass with 7 / 10 to unlock your certificate.

1. 1. What is the output of: console.log(typeof null)?

   'null''object''undefined''boolean'

2. 2. Which of these creates a true block-scoped variable?

   varletfunctionthis

3. 3. What does [] + [] evaluate to in JavaScript?

   0'[]'''NaN

4. 4. Which method returns a new array without mutating the original?

   pushsplicemapsort

5. 5. What is the result of: 0.1 + 0.2 === 0.3?

   truefalseundefinedTypeError

6. 6. Which keyword guarantees a function call's `this` value?

   callbindapplyFunction

7. 7. What does Promise.all reject with?

   An array of errorsThe first rejection reasonundefinedAll rejection reasons

8. 8. Which is NOT a valid way to clone an object shallowly?

   {...obj}Object.assign({}, obj)JSON.parse(JSON.stringify(obj))Object.clone(obj)

9. 9. What is hoisting?

   Moving declarations to the top of their scopeA type coercion ruleAn optimisation in V8A way to import modules

10. 10. Which event loop phase runs setTimeout callbacks?

    microtasktimerspollrender