The size accessor property of Set instances returns the number of (unique) elements in this set.
Description
The value of size is an integer representing how many entries the Set object has. A set accessor function for size is undefined; you cannot change this property.
Examples
Using size
const mySet = new Set();
mySet.add(1);
mySet.add(5);
mySet.add("some text");
console.log(mySet.size); // 3