JavaScript ES6+ Logic Challenge

Challenge your JS skills with array methods, closures, promises, async/await, hoisting, and modern ES6+ syntax.

5 Questions 15 Minutes Instant Scoring All Quizzes

Question 1 of 5

00:00

1. What does Array.prototype.map() return in JavaScript?

const nums = [1, 2, 3];

const res = nums.map(x => x * 2);

A The original mutated array B A new array populated with transformed values C A single aggregated number D A boolean flag

2. What is the output of typeof null in JavaScript?

console.log(typeof null);

A "null" B "undefined" C "object" D "boolean"

3. Which keyword declares block-scoped variables that cannot be reassigned?

______ PI = 3.14159;

A var B let C const D static

5. What is a Closure in JavaScript?

function makeCounter() {

  let count = 0;

  return () => ++count;

}

A A way to close browser windows B A function bundled with access to its outer lexical scope C A syntax error in async functions D A method that terminates loops

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JavaScript ES6+ Logic Challenge

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JavaScript ES6+ Logic Challenge

1. What does Array.prototype.map() return in JavaScript?

2. What is the output of typeof null in JavaScript?

3. Which keyword declares block-scoped variables that cannot be reassigned?

4. How do you handle errors and rejected Promises when using async/await syntax?

5. What is a Closure in JavaScript?

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