Question

What's the output?

const set = new Set([1, 1, 2, 3, 4]);

console.log(set);

• A: [1, 1, 2, 3, 4]
• B: [1, 2, 3, 4]
• C: {1, 1, 2, 3, 4}
• D: {1, 2, 3, 4}

Answer 1

Answer: D

The Set object is a collection of unique values: a value can only occur once in a set.

We passed the iterable [1, 1, 2, 3, 4] with a duplicate value 1. Since we cannot have two of the same values in a set, one of them is removed. This results in {1, 2, 3, 4}.