You can create a new Set in JavaScript using the Set constructor. Here's how you can do it:

const mySet = new Set();

In the above code, mySet is a new Set that is initially empty. You can also create a Set with an iterable, such as an array or another Set, by passing it as an argument to the Set constructor. For example:

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

This creates a new Set called mySet with the elements 1, 2, 3, and 4. The Set will automatically eliminate any duplicate values, so you'll end up with a Set containing unique elements.

You can also add elements to the Set later using the add method:

mySet.add(5);
mySet.add(6);

Now, mySet contains the elements 1, 2, 3, 4, 5, and 6.

Sets in JavaScript are a useful data structure for maintaining collections of unique values, and they provide various methods for adding, removing, and checking the existence of elements.