var mySet = new Set(); mySet.add(1); // Set [ 1 ] mySet.add(5); // Set [ 1, 5 ] mySet.add(5); // Set [ 1, 5 ] mySet.add('some text'); // Set [ 1, 5, 'some text' ] var o = {a: 1, b: 2}; mySet.add(o); mySet.add({a: 1, b: 2}); // o is referencing a different object so this is okay mySet.has(1); // true mySet.has(3); // false, 3 has not been added to the set mySet.has(5); // true mySet.has(Math.sqrt(25)); // true mySet.has('Some Text'.toLowerCase()); // true mySet.has(o); // true mySet.size; // 5 mySet.delete(5); // removes 5 from the set mySet.has(5); // false, 5 has been removed mySet.size; // 4, we just removed one value console.log(mySet);// Set [ 1, "some text", Object {a: 1, b: 2}, Object {a: 1, b: 2} ]