IMDB Season Rating

IMDBSeasonRating.user.js

// ==UserScript==
// @name         IMDB Season Rating
// @namespace    http://ahmetkun.com/
// @version      0.1
// @description  calculate the rating of a tv show's seasons by episode ratings.
// @author       Ahmet Kun
// @match        http://www.imdb.com/title/*/eprate*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var seasons = {};
    var output = '';
    document.querySelectorAll('#tn15content table:first-of-type tr').forEach(function(el, i) {
        if(!i) return;
        var tds = el.querySelectorAll('td'),
            epNum = tds[0].textContent,
            season = epNum.split('.')[0],
            rating = parseFloat(tds[2].textContent);
        if(!seasons[season]) seasons[season] = [];
        seasons[season].push(rating);
    });

    for(var season in seasons) {
        var len = seasons[season].length,
            sum = seasons[season].reduce(function(a,b) {return a + b}, 0);
        output += '<tr>' +
            '<td>Season ' + season + '</td>' +
            '<td align="right">' + parseFloat(sum/len).toFixed(2) + '</td>' +
            '<td align="right">' + len + '</td>' +
        '</tr>';
    }
    var insertEl = document.createElement('table');
    insertEl.innerHTML = '<tr><th>Season</th><th>Average Rating</th><th>Num. of episodes rated</th></tr>' + output;
    document.querySelectorAll('#tn15content')[0].insertBefore(insertEl, document.querySelectorAll('#tn15content h3:first-of-type')[0]);
})();