Ways to create a Set in JavaScript?

Question

In Eloquent JavaScript, Chapter 4, a set of values is created by creating an object and storing the values as property names, assigning arbitrary values (e.g. true) as property

Answer 1

The first way is idiomatic JavaScript.

Any time you want to store a key/value pair, you must use a JavaScript object. As for arrays, there are several problems:

1. The index is a numerical value.

2. No easy way to check to see if a value is in an array without looping through.

3. A set doesn't allow duplicates. An array does.