Edit in JSFiddle

var mySet = new Set([1,2,3,4,5]);
console.log('init =>',[...mySet]);

mySet.delete(4); // Set [1, 2, 3, 5]
console.log('on delete(4) =>',[...mySet]);

mySet.clear(); // Set []
console.log('on clear() =>' ,[...mySet]);