Adds an estimate of "hotness" to the question sidebar, calculated using the formula from http://meta.stackexchange.com/a/61343. Questions with a high hotness value may be selected for the Hot Network Questions list. Note that the hotness value displayed by this script does not include the per-site scaling factors, and so does not match the "arbi…

se_hotness_estimator.user.js

// ==UserScript==
// @name        Stack Exchange hotness estimator
// @namespace   http://vyznev.net/
// @description Estimates how highly each Stack Exchange question would rank on the Hot Network Questions list
// @author      Ilmari Karonen
// @version     0.3.3
// @license     Public domain
// @homepageURL http://meta.stackexchange.com/a/284933
// @match       *://*.stackexchange.com/questions/*
// @match       *://*.stackoverflow.com/questions/*
// @match       *://*.superuser.com/questions/*
// @match       *://*.serverfault.com/questions/*
// @match       *://*.stackapps.com/questions/*
// @match       *://*.mathoverflow.net/questions/*
// @match       *://*.askubuntu.com/questions/*
// @grant       none
// ==/UserScript==

(function() {
    'use strict';

    var voteCount = document.querySelector('#question .js-vote-count');
    var creationTimeStamp = document.querySelector('#qinfo .label-key[title^="20"][title$=Z]');
    if ( ! voteCount || ! creationTimeStamp ) return;

    var now = new Date ();
    var questionScore = Number(voteCount.textContent);
    var qCreationTime = new Date(creationTimeStamp.getAttribute('title'));
    var qAgeInHours = (now.getTime() - qCreationTime.getTime()) / (1000*60*60);

    var answerScores = document.querySelectorAll('.answer:not(.deleted-answer) .js-vote-count');
    var answerCount = answerScores.length;
    var answerScore = 0;
    for (var i = 0; i < answerScores.length; i++) answerScore += Number(answerScores[i].textContent);

    // http://meta.stackexchange.com/questions/60756/how-do-the-arbitrary-hotness-points-work-on-the-new-stack-exchange-home-page
    // The conversion to percentages below is completely arbitrary, but seems to yield reasonable-looking values (i.e. around 100% for actual HNQs).
    var hotness = ((Math.min(answerCount, 10) * questionScore) / 5 + answerScore) / Math.pow(Math.max(qAgeInHours + 1, 6), 1.4);

    var oldRow = document.querySelector('#qinfo tr'), newRow = oldRow.cloneNode(true);
    var cells = newRow.querySelectorAll('td');
    cells[0].innerHTML = '<p class="label-key">hotness</p>';
    cells[1].innerHTML = '<p class="label-key" title="The relative hotness score of this question is approximately ' + hotness.toPrecision(5) + '."><b>' + Math.round(100 * hotness) + '%</b></p>';
    oldRow.parentNode.appendChild(newRow);
} )();