set.js

var s = new Set();
s.add(1).add(2).add(1);

console.log('Size of s => ', s.size); // 2
console.log('s has 2 => ', s.has(2)); // true

s.delete(2);
console.log('s has 2 => ', s.has(2)); // false

s.clear();
console.log('s => ', s);              // Set {}