JSON stringify a Set

Question

How would one JSON.stringify() a Set?

Things that did not work in Chromium 43:

var s = new Set([\'foo\', \'bar\']);

JSON.stringify(s); // -> \"{}         


        

Answer 1

Use this JSON.stringify replacer:

(because toJSON is a legacy artifact, and a better approach is to use a custom replacer, see https://github.com/DavidBruant/Map-Set.prototype.toJSON/issues/16)

function Set_toJSON(key, value) {
  if (typeof value === 'object' && value instanceof Set) {
    return [...value];
  }
  return value;
}

Then:

const fooBar = { foo: new Set([1, 2, 3]), bar: new Set([4, 5, 6]) };
JSON.stringify(fooBar, Set_toJSON)

Result:

"{"foo":[1,2,3],"bar":[4,5,6]}"