How to use the request-promise.jar function in request-promise

function addCookie(req, key, value) {
  const cookie = request.cookie(`${key}=${value}`);
  const jar = request.jar();
  jar.setCookie(cookie, req.uri.split('?')[0]);
  req.jar = jar;
  return req;
}

return new Promise(function(resolve, reject) {
                fs.unlinkSync("pc-cookie.json");
                cookieJar = request.jar(new cookieStore('./pc-cookie.json'));
                this.csrf = null;
                resolve();
        });
}

constructor (setting) {
		this.setCookieJar(request.jar());
		this.setScope(setting.scope || fullScopes);

		for (var key of ['app','key','login','phone','pass','version','proxy']) {
			this[key] = setting[key] || null;
		}

		if (this.login === null) {
			this.login = this.phone;
		}

		this._capthaHandler = null;
		this._twoFactorHandler = null;
	}

constructor (vk) {
		this.vk = vk;

		this.jar = request.jar();

		this._captchaAttempts = 0;
	}