const YahooFantasy = require('yahoo-fantasy');
const yf = new YahooFantasy(
  Y!APPLICATION_KEY,
  Y!APPLICATION_SECRET,
  tokenCallbackFn, // optional
  redirectUri // optional
);

yf.setUserToken(
  Y!OAuthAccessToken
);

// promise based
try {
  const game_weeks = await yf.game.game_weeks(game_key);
} catch (e) {
  // handle error
}

// callback based
yf.game.game_weeks(game_key, callbackFn);

{
  "game_key": "328",
  "game_id": "328",
  "name": "Baseball",
  "code": "mlb",
  "type": "full",
  "url": "http://baseball.fantasysports.yahoo.com/b1",
  "season": "2014",
  "weeks": [
    {
      "week": "1",
      "start": "2014-03-22",
      "end": "2014-04-06"
    },
    {
      "week": 2,
      "start": "2014-04-07",
      "end": "2014-04-13"
    },
    {
      "week": 3,
      "start": "2014-04-14",
      "end": "2014-04-20"
    },
    {
      "week": 4,
      "start": "2014-04-21",
      "end": "2014-04-27"
    },
    {
      "week": 5,
      "start": "2014-04-28",
      "end": "2014-05-04"
    },
    {
      "week": 6,
      "start": "2014-05-05",
      "end": "2014-05-11"
    },
    {
      "week": 7,
      "start": "2014-05-12",
      "end": "2014-05-18"
    },
    {
      "week": 8,
      "start": "2014-05-19",
      "end": "2014-05-25"
    },
    {
      "week": 9,
      "start": "2014-05-26",
      "end": "2014-06-01"
    },
    {
      "week": 10,
      "start": "2014-06-02",
      "end": "2014-06-08"
    },
    {
      "week": 11,
      "start": "2014-06-09",
      "end": "2014-06-15"
    },
    {
      "week": 12,
      "start": "2014-06-16",
      "end": "2014-06-22"
    },
    {
      "week": 13,
      "start": "2014-06-23",
      "end": "2014-06-29"
    },
    {
      "week": 14,
      "start": "2014-06-30",
      "end": "2014-07-06"
    },
    {
      "week": 15,
      "start": "2014-07-07",
      "end": "2014-07-20"
    },
    {
      "week": 16,
      "start": "2014-07-21",
      "end": "2014-07-27"
    },
    {
      "week": 17,
      "start": "2014-07-28",
      "end": "2014-08-03"
    },
    {
      "week": 18,
      "start": "2014-08-04",
      "end": "2014-08-10"
    },
    {
      "week": 19,
      "start": "2014-08-11",
      "end": "2014-08-17"
    },
    {
      "week": 20,
      "start": "2014-08-18",
      "end": "2014-08-24"
    },
    {
      "week": 21,
      "start": "2014-08-25",
      "end": "2014-08-31"
    },
    {
      "week": 22,
      "start": "2014-09-01",
      "end": "2014-09-07"
    },
    {
      "week": 23,
      "start": "2014-09-08",
      "end": "2014-09-14"
    },
    {
      "week": 24,
      "start": "2014-09-15",
      "end": "2014-09-21"
    },
    {
      "week": 25,
      "start": "2014-09-22",
      "end": "2014-09-28"
    }
  ]
}