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     0.3.4
// @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 infobar = document.querySelector('#question-header + .grid');  // no id :(
    if ( ! voteCount || ! infobar ) return;

    var creationTimeStamp = infobar.querySelector('time[itemprop=dateCreated]');
    if ( ! creationTimeStamp ) return;

    var now = new Date ();
    var questionScore = Number(voteCount.textContent);
    var qCreationTime = new Date(creationTimeStamp.getAttribute('datetime'));
    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 = infobar.lastElementChild, newRow = oldRow.cloneNode(false), keySpan = oldRow.firstElementChild.cloneNode(false);

    keySpan.textContent = 'Hotness';
    newRow.innerHTML = ' <span title="The relative hotness score of this question is approximately ' + hotness.toPrecision(5) + '.">' + Math.round(100 * hotness) + '%</span>';
    newRow.insertBefore(keySpan, newRow.firstChild);

    oldRow.className += ' mr16';
    infobar.appendChild(newRow);
} )();