How to use setprototypeof - 3 common examples

function createCrawler(base: string, options: Object = {}): Object {
  if (typeof base !== "string") {
    throw new Error(`Base must be a string, not ${typeof base}`);
  }

  const config: Object = {
    interval: 250,
    concurrent: 10,
    ...options
  };

  // Will be used by retry-request:
  const requestJar = request.jar();
  const requestObj = request.defaults({ jar: requestJar, ...config });
  setPrototypeOf(requestObj, requestJar);

  // Crawler base:
  const crawler: Object = {
    base: base,
    opts: config,
    req: SpiderRequest,
    res: SpiderResponse,
    request: requestObj
  };

  // Glues all the components together:
  mixin(crawler, SpiderQueue, false);
  mixin(crawler, SpiderRouter, false);
  mixin(crawler, EventEmitter.prototype);

  return crawler;

retryRequest(uri, { request: this.request }, (error, response) => {
        if (error || response.statusCode !== 200) {
          return reject(error || uri);
        }

        const req: Object = {};
        const res: Object = response;

        // Set circular references:
        res.req = req;
        req.res = res;

        // Alter the prototypes:
        setPrototypeOf(req, this.req);
        setPrototypeOf(res, this.res);

        resolve({ req, res, uri });
      });
    });

retryRequest(uri, { request: this.request }, (error, response) => {
        if (error || response.statusCode !== 200) {
          return reject(error || uri);
        }

        const req: Object = {};
        const res: Object = response;

        // Set circular references:
        res.req = req;
        req.res = res;

        // Alter the prototypes:
        setPrototypeOf(req, this.req);
        setPrototypeOf(res, this.res);

        resolve({ req, res, uri });
      });
    });