polyfill to support serializing a JS Set

set.toJSON.js

// 2 August 2023
// set.toJSON
// when you absolutely must serialize a set
// using JSON.stringify() which normally
// returns set: {}

Set.prototype.toJSON = function toJSON() {
  var set = {};
  for (var [k, v] of this.entries()) {
    set[k] = v;
  }
  return set;
}

/* test it out */

var o = { set: new Set(['1', 'X']) };
o.set.add("K");
o.set.add(0);

console.log(o);
// { set: Set(4) [ "1", "X", "K", "0" }

JSON.stringify(o, null, 2);
/*
'{
  "set": {
    "0": 0,
    "1": "1",
    "X": "X",
    "K": "K"
  }
}'
*/