Shuffle button for js13kGames voting page

js13kgames_vote_shuffle.js

// ==UserScript==
// @name         Shuffle button for js13kGames voting page
// @namespace    https://github.com/gheja/
// @version      0.1
// @description  try to take over the world!
// @author       gheja, nes
// @match        https://dev.js13kgames.com/games
// @icon         https://www.google.com/s2/favicons?sz=64&domain=js13kgames.com
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    // based on code by @nes, thanks!

    // NOTE: switching categories break the order

    let sort_storage_key = "sort_seed";

    function sortRun(n) {
        if (n === undefined)
        {
            n = localStorage.getItem(sort_storage_key);
        }

        if (n === null) {
            // do not shuffle initially
            return;
        }

        let rnd = parseInt(n);

        function randPrngSeed() {
            let mod = 2 ** 31 - 1;
            rnd = 16807 * rnd % mod;
            return (rnd - 1) / (mod - 1);
        }

        function arrRandSort(arr) {
            for (let i = arr.length - 1; i > 0; i--) {
                let j = Math.floor(randPrngSeed() * (i + 1));
                let tmp = arr[i];
                arr[i] = arr[j];
                arr[j] = tmp;
            }
        }

        function arrSortByLink(arr) {
            arr.sort((a, b) => {
                return a.href.localeCompare(b.href);
            });
        }

        var games = document.getElementById("g-games");
        var gamesChildren = Array.from(document.getElementById("g-games").childNodes);
        arrSortByLink(gamesChildren);
        arrRandSort(gamesChildren);

        while (games.firstChild) {
            games.removeChild(games.firstChild);
        }

        games.append(...gamesChildren);
    }

    function sortShuffle() {
        let n = Math.floor(Math.random() * 10000);
        localStorage.setItem(sort_storage_key, n);

        // localstorage does not update immediately
        sortRun(n);
    }

    function attemptToSort() {
        if (document.getElementById("g-games").childNodes.length == 0) {
            window.setTimeout(attemptToSort.bind(), 50);
            return;
        }

        sortRun();
    }

    function sortInit() {
        let tmp = document.createElement("div");
        tmp.className = "btn";
        tmp.addEventListener("click", sortShuffle.bind());
        tmp.innerHTML = "Shuffle";
        document.getElementById("g-categories").appendChild(tmp);

        // the entries are not yet loaded when "load" fires
        attemptToSort();
    }

    window.addEventListener('load', sortInit);
})();