Given a rank of a day, find the right work on Pixiv.

pixiv-rank.js

/*** Dependencies ************************************************************/
const Promise = require('bluebird');
const jsEnv = Promise.promisify(require('jsdom').env);

/*** The Function ************************************************************/
const getLinksByRank = (date, rank) =>
  jsEnv('http://www.pixiv.net/ranking.php?mode=daily&date=' + date)
    .then(window => window.document.getElementById(rank).getElementsByClassName('work')[0].href)
    .then(jsEnv)
    .then(window => window.document.getElementsByClassName('_work')[0].getElementsByTagName('img')[0].src)
const linkPreviewToOrigin = preview =>
  'http://i1.pixiv.net/img-original/img/' + preview.match(/\d{4}(?:\/\d{2}){5}\/\d+_p\d+/)[0] + '.jpg';

/*** Usage *******************************************************************/
const log = console.log.bind(console);
getLinksByRank('20160505', 1)
  .tap(log)   // Link for preview.
  .then(linkPreviewToOrigin)
  .tap(log);  // Link for origin. Need to set REFERER to download.