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JavaScript Objective Questions and Answers

Practice JavaScript objective questions with answers and clear explanations. Covers core JavaScript, ES6+, closures, scope, hoisting, async programming, promises, event loop, prototypes, memory management, and advanced language concepts.

This JavaScript quiz contains carefully curated objective questions with correct answers and clear explanations. It is designed for frontend and backend developers, interview preparation, and deep understanding of modern JavaScript concepts including ES6+, asynchronous behavior, scope, closures, and performance pitfalls.

Practice JavaScript MCQs with Detailed Explanations

Answer at least 12 questions to submit.

31.
What will be logged? console.log(typeof undefined == typeof null);
Medium
32.
Which pattern helps prevent memory leaks with event listeners?
High
33.
What does Promise.all() do if one Promise rejects?
High
34.
Which scenario creates a closure?
Medium
35.
What is the output? console.log(+true);
Medium
36.
Which statement about async/await is true?
High
37.
What is the output? console.log([] === []);
Medium
38.
Which structure is most likely to cause a memory leak?
High
39.
What does the call stack manage?
Medium
40.
Which operation is synchronous?
Medium
41.
What will be logged? console.log(typeof function(){});
Medium
42.
Which can prevent accidental global variables?
Medium
43.
What happens if await is used outside async?
Medium
44.
What is the output? console.log(null + 1);
Medium
45.
Which tool helps avoid memory leaks in key-value storage?
High
Answered: 0 / 15

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