JavaScript implementation of Python's defaultdict using Proxy and Reflect

defaultdict.js

const defaultdict = (getDefault) =>
  new Proxy(
    {},
    {
      get: (target, key) => {
        if (!Reflect.has(target, key))
          Reflect.set(
            target,
            key,
            typeof getDefault === "function" ? getDefault() : getDefault
          );
        return Reflect.get(target, key);
      },
    }
  );

export default defaultdict;

examples.js

import defaultdict from "./defaultdict";

const dict1 = defaultdict(Number);
dict1.a = dict1.a + 1;

const dict2 = defaultdict(Array);
dict2.a.push("hello world");
dict2.b.push("foo bar");

const ejected2 = { ...dict2 };