jsch9.js

// sets
let exampleSet = new Set();

// has one property - size
exampleSet.add(1); // exampleSet: Set {1}
exampleSet.add(1); // exampleSet: Set {1}
exampleSet.add(2); // exampleSet: Set {1, 2}

// deletion
exampleSet.delete(1); // true, exampleSet: Set {2}

// contains
exampleSet.add(1);
exampleSet.has(1); // true
exampleSet.has(2); // true
exampleSet.has(3); // false

let intersects = (A, B) => new Set(Array.from(A).filter(a => B.has(a)));
let union = (A, B) => new Set(Array.from(A).concat(Array.from(B)));

// performs A - B
let difference = (A, B) => new Set(Array.from(A).filter(a => !(B.has(a))));

let setA = new Set([1, 2, 3, 4]);
let setB = new Set([2, 3]);
console.log(intersects(setA, setB));

let setC = new Set([5, 6]);
console.log(union(setA, setC));

console.log(difference(setA, setB));