选择困难症患者专用的 Chrome 脚本，在豆瓣阅读征文大赛作品列表里随机挑一本作品

pick-works.js

// ==UserScript==
// @name         pick-works
// @namespace    http://tampermonkey.net/
// @version      0.1
// @author       E.T
// @match        https://read.douban.com/competition/2015/works*
// @grant        none
// ==/UserScript==

;(function () {
  'use strict';

  function randInt(upper) {
    return Math.floor(Math.random() * upper) // [0, upper)
  }

  function pick(upper, prevIdx) {
    var idx = randInt(upper)

    while (idx === prevIdx) {
      idx = randInt(upper)
    }

    return idx
  }

  Do(function () {
    var btnParent = $('.works-filter .inner')
      , items = $('.works-list .item')
      , idxUpper = items.length
      , prevIdx
      , prevItem

    btnParent.append('<a href="#" class="btn btn-pick active">给大爷挑一个</a>')

    btnParent.click('.btn-pick', function (evt) {
      evt.preventDefault()

      var idx = pick(idxUpper, prevIdx)
        , item = $(items[idx])

      if (prevItem !== undefined) {
        prevItem.hide()
        item.show()
      } else {
        for (var i = 0; i < idxUpper; ++i) {
          if (i === idx) { continue }
          $(items[i]).hide()
        }
      }

      prevIdx = idx
      prevItem = item
    })
  })
})();