Question 1 of 5
Quiz library
About 3 minutes
Need a teammate, not a test?
Build something great with a JavaScript expert.
Study guide
JavaScript quiz questions and answers
Review all 5 questions at your own pace. Open each answer to see the correct response and a concise explanation of the concept.
1What does a Promise represent in JavaScript?
Correct answer
A future async result
Promises represent asynchronous work that may resolve or reject later.
2What is a closure?
Correct answer
A function retaining access to its outer scope
Closures let functions use variables from the scope where they were created.
3Which keyword declares a block-scoped variable?
Correct answer
let
let and const are block-scoped, while var is function-scoped.
4What does event delegation rely on?
Correct answer
Event bubbling
Event delegation attaches one handler to a parent and handles events bubbled from children.
5What can block user interactions in the browser?
Correct answer
Long-running JavaScript on the main thread
Heavy synchronous JavaScript prevents the browser from responding quickly to input.