comparing ECMA6 sets for equality

You can also try:

var a = new Set([1,2,3]);
var b = new Set([1,3,2]);

let areSetsEqual = (a, b) => a.size === b.size && [...a].every(value => b.has(value));

console.log(areSetsEqual(a,b)) 

Try this:

const eqSet = (xs, ys) =>
    xs.size === ys.size &&
    [...xs].every((x) => ys.has(x));

const ws = new Set([1, 2, 3]);
const xs = new Set([1, 3, 2]);
const ys = new Set([1, 2, 4]);
const zs = new Set([1, 2, 3, 4]);

console.log(eqSet(ws, xs)); // true
console.log(eqSet(ws, ys)); // false
console.log(eqSet(ws, zs)); // false