JavaScript Advanced Test

Challenge your understanding of promises, object behavior, async functions and modern operators.

6 questions. Choose the best answer for each question, then review every explanation.

Question 1 of 6

1 of 6

Question 1Which value is logged first after "start"?

console.log('start');
setTimeout(() => console.log('timeout'), 0);
Promise.resolve().then(() => console.log('promise'));

"promise""timeout"They always appear togetherThe order is random

Question 2What kind of copy does object spread create?

const copy = { ...original };

A frozen copyA reference to the same objectA shallow copyA recursive deep copy

Question 3What does optional chaining return when the value before ?. is null or undefined?

profile.address?.city

undefinednullfalseAn empty string

Question 4When does the nullish coalescing operator use its right-hand value?

value ?? fallback

Only when value is falseOnly when value is zeroWhen value is null or undefinedWhenever value is falsy

Question 5What does an async function always return?

A generatorA callbackA synchronous primitiveA Promise

Question 6Which statement about Object.freeze() is correct?

It converts the object into JSONIt is shallow unless nested objects are frozen separatelyIt recursively freezes all nested valuesIt prevents the object from being read