What does a Promise represent in JavaScript?
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Question 1 of 5
JavaScript quiz
Review JavaScript essentials including async code, closures, modules, DOM, and performance.
Frontend · About 3 minutes
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.
Topics covered
- Promises
- Closures
- Block scope
- Event delegation
- Main-thread performance
Related developer quizzes
What does a Promise represent in JavaScript?
Correct answer
A future async result
Promises represent asynchronous work that may resolve or reject later.
What 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.
Which keyword declares a block-scoped variable?
Correct answer
let
let and const are block-scoped, while var is function-scoped.
What does event delegation rely on?
Correct answer
Event bubbling
Event delegation attaches one handler to a parent and handles events bubbled from children.
What 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.
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