JS: Set.prototype.union

(new in JS: ECMAScript 2024)

setA.union(setB)

• return the union of 2 sets.
• setB can be a Map.

const xx = new Set([4, 5, 6])
const yy = new Set([6, 7, 8])
console.log(xx.union(yy))
// Set(5) { 4, 5, 6, 7, 8 }

// union of 2 map's keys

const mapA = new Map([[4, 0], [5, 0], [6, 0]])
const mapB = new Map([[6, 0], [7, 0], [8, 0]])

console.log((new Set(mapA.keys())).union(mapB))
// Set(5) { 4, 5, 6, 7, 8 }