StarGiveaways.user.js

// ==UserScript==
// @name StarGiveaways
// @namespace StarGiveaways
// @description ONLY adds the ability to see ESGST giveaways.
// @version 0.0.1
// @author revilheart
// @contributor Royalgamer06
// @contributor q00u
// @match https://www.steamgifts.com/*
// @match https://www.steamtrades.com/*
// @grant none
// @require https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js
// @noframes
// ==/UserScript==

try {
    var matches = document.querySelectorAll(`[href^="ESGST-"]`);
    var n = matches.length;
    if (n > 0) {
        for (var i = 0; i < n; ++i) {
            var code = matches[i].getAttribute(`href`).match(/ESGST-(.+)/)[1];
            var decodedCode = decodeGiveawayCode(code);
            var html = `<a href="/giveaway/${decodedCode}/">/giveaway/${decodedCode}/</a><br/>`;
            var actions = matches[i].closest(`.comment`).getElementsByClassName(`comment__actions`)[0];
            html = `
                <a class="esgst-eg" href="/giveaway/${decodedCode}/" title="ESGST Exclusive Giveaway">
                    <i class="fa fa-spin fa-star"></i>
                </a>
            `;
            actions.insertAdjacentHTML(`beforeEnd`, html);
        }
    }
} catch (error) {
    console.log(error);
    window.alert(`StarGiveaways has failed to load. Check the console for more info.`);
}

function decodeGiveawayCode(code) {
    var decodedCode = ``;
    var separatedCode = code.split(`-`);
    for (var i = 0, n = separatedCode.length; i < n; ++i) {
        decodedCode += String.fromCharCode(parseInt(separatedCode[i], 16));
    }
    return rot(decodedCode, 13);
}

function rot(string, n) {
    return string.replace(/[a-zA-Z]/g, function (char) {
        return String.fromCharCode(((char <= `Z`) ? 90 : 122) >= ((char = char.charCodeAt(0) + n)) ? char : (char - 26));
    });
}