​MDN​
Use Set.add
vs Map.set
Use Set.size
vs Array.length
To remove/delete: use delete
const new = new Set(old);
Or if enabled:
const new = ...old
for (let value of set.values()) {...}
Array.from(new Set())
​https://github.com/aizatto/nodejs/blob/master/src/fn.js#L42​
function setMath<T>(a: Set<T>, b: Set<T>) {return {remove: [...a].filter(x => !b.has(x)),add: [...b].filter(x => !a.has(x)),};}