Runtypes definition to match JSON

json-as-runtypes.ts

import * as rt from 'runtypes';

export type JSONPrimitive = string | number | boolean | null;
export type JSONValue = JSONPrimitive | JSONObject | JSONArray;
export type JSONObject = { [member: string]: JSONValue };
export type JSONArray = Array<JSONValue>;
type JSONRoot = JSONArray | JSONObject;

const JSONPrimitiveRt = rt.Intersect(rt.String, rt.Number, rt.Boolean, rt.Null);
const JSONValueRt: rt.Runtype<JSONValue> = rt.Lazy(() =>
  rt.Intersect(JSONPrimitiveRt, JSONObjectRt, JSONArrayRt),
);
const JSONObjectRt: rt.Runtype<JSONObject> = rt.Lazy(() =>
  rt.Dictionary(JSONValueRt),
);

const JSONArrayRt: rt.Runtype<JSONArray> = rt.Lazy(() => rt.Array(JSONValueRt));

const JSONRootRt = rt.Intersect(JSONObjectRt, JSONArrayRt);