JSON decycle

decycle.js

const replaceSetMap = (object) => {
  if (object) {
    if (object.constructor === Set) return [...object];
    if (object.constructor === Map) return Object.fromEntries(object);
  }
  return object;
};

const decycle = (rootObject, { replacer = replaceSetMap, seen = new WeakMap() } = {}) => {
  const _decycle = (object, path = "$") => {
    if (replacer !== undefined) object = replacer(object);

    let ctor;
    if (!object || !(ctor = object.constructor) || ctor === Number || ctor === String || ctor === Boolean || ctor === RegExp || ctor === Date || ctor === RegExp || typeof object !== "object") return object;

    if (seen.has(object)) return { $ref: seen.get(object) };
    seen.set(object, path);

    if (ctor === Array) return object.map((value, key) => _decycle(value, `${path}[${key}]`));

    const result = { ...object };
    for (const key in result) result[key] = _decycle(result[key], `${path}[${JSON.stringify(key)}]`);
    return result;
  };
  return _decycle(rootObject);
};

const stringify = (rootObject, { replacer = replaceSetMap, seen = new WeakMap(), result = "" } = {}) => {
  const _stringify = (object, path = "$") => {
    if (replacer !== undefined) object = replacer(object);

    let ctor;
    if (object === undefined) return null; // undefined is not a valid JSON value
    if (object === null || !(ctor = object.constructor) || ctor === Number || ctor === String || ctor === Boolean || ctor === RegExp || ctor === Date || ctor === RegExp || typeof object !== "object") {
      result += JSON.stringify(object) ?? '"' + object.toString() + '"';
      return;
    }

    if (seen.has(object)) {
      result += `{"$ref":${JSON.stringify(seen.get(object))}}`;
      return;
    }
    seen.set(object, path);

    if (ctor === Array) {
      result += "[";
      let first = true;
      for (let key = 0; key < object.length; ++key) {
        if (first) first = false;
        else result += ",";
        _stringify(object[key], `${path}[${key}]`);
      }
      result += "]";
      return;
    }

    result += "{";
    let first = true;
    for (const key in object) {
      const keyStr = JSON.stringify(key);
      if (first) first = false;
      else result += ",";
      result += keyStr;
      result += ":";
      _stringify(object[key], `${path}[${keyStr}]`);
    }
    result += "}";
  };
  _stringify(rootObject);
  return result;
};