code: function FastObject() {
    // A prototype object will have "fast properties" enabled once it is checked
    // against the inline property cache of a function, e.g. fastProto.property:
    // https://github.com/v8/v8/blob/6.0.122/test/mjsunit/fast-prototype.js#L48-L63
    if (fastProto !== null && typeof fastProto.property) {
      const result = fastProto;
      fastProto = FastObject.prototype = null;
      return result;
    }
    fastProto = FastObject.prototype = Object.create(null);
    return new FastObject;
  }
docs: Creates an object with permanently fast properties in V8. See Toon Verwaest's post https://medium.com/@tverwaes/setting-up-prototypes-in-v8-ec9c9491dfe2#5f62 for more details. Use %HasFastProperties(object) and the Node flag --allow-natives-syntax to check whether an object has fast properties.