tamper.js

// ==UserScript==
// @name         Zulip
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://macandcheese.zulipchat.com
// @icon         https://www.google.com/s2/favicons?sz=64&domain=youtube.com
// @grant        none
// ==/UserScript==

(function () {
    "use strict";

    function get_header() {
        function header() {
            return document.querySelector("#top_navbar");
        }

        function logo() {
            const elem = header().querySelector(".column-left");

            return { elem };
        }

        function search_bar() {
            const elem = header().querySelector(".top-navbar-container");

            return { elem };
        }

        const elem = header();

        return { logo, search_bar };
    }

    function get_app() {
        function app() {
            return document.querySelector(".app");
        }

        function left_sidebar() {
            function shortcuts() {
                const elem = parent.querySelector("#global_filters");
                return { elem };
            }

            function dm_list() {
                function header() {
                    function title() {
                        const elem = parent.querySelector("h4");
                        return { elem };
                    }

                    // ANNOYINGLY, the header is not part of the list, so we
                    // use parent.
                    const elem = parent.querySelector(
                        "#private_messages_section_header"
                    );
                    return { elem, title };
                }

                const elem = parent.querySelector("#private_messages_list");
                return { elem, header };
            }

            function streams_list() {
                function header() {
                    function title() {
                        const elem = lst.querySelector("h4");
                        return { elem };
                    }

                    const elem = lst.querySelector("#streams_header");
                    return { elem, title };
                }

                const elem = parent.querySelector("#streams_list");
                const lst = elem;
                return { elem, header };
            }

            const elem = app().querySelector("#left-sidebar");
            const parent = elem;
            return { elem, shortcuts, dm_list, streams_list };
        }

        function middle_panel() {
            function message_list() {
                const elem = parent.querySelector("#zfilt");

                return { elem };
            }

            function bottom_whitespace() {
                const elem = parent.querySelector("#bottom_whitespace");

                return { elem };
            }

            function compose_box() {
                const elem = parent.querySelector("#compose-content");

                return { elem };
            }

            const elem = app().querySelector(".column-middle-inner");

            const parent = elem;
            return { elem, message_list, bottom_whitespace, compose_box };
        }

        function right_sidebar() {
            function shortcuts() {
                const elem = app().querySelector(".right-sidebar-shortcuts");

                return { elem };
            }

            const elem = app().querySelector("#right-sidebar");
            return { elem, shortcuts };
        }

        return { left_sidebar, middle_panel, right_sidebar };
    }

    function tamper() {
        function style(elem, f, v) {
            elem.style[f] = v;
        }

        const { logo, search_bar } = get_header();
        style(logo().elem, "background", "khaki");
        style(search_bar().elem, "background", "darkseagreen");

        const { left_sidebar, middle_panel, right_sidebar } = get_app();

        style(left_sidebar().shortcuts().elem, "background", "blanchedalmond");

        style(
            left_sidebar().dm_list().header().elem,
            "background",
            "cadetblue"
        );
        style(left_sidebar().dm_list().header().title().elem, "color", "red");
        style(left_sidebar().dm_list().elem, "background", "khaki");

        style(
            left_sidebar().streams_list().header().elem,
            "background",
            "cadetblue"
        );
        style(
            left_sidebar().streams_list().header().title().elem,
            "color",
            "red"
        );
        style(left_sidebar().streams_list().elem, "background", "khaki");

        style(middle_panel().elem, "background", "khaki");
        style(middle_panel().message_list().elem, "background", "cadetblue");
        style(
            middle_panel().bottom_whitespace().elem,
            "background",
            "deepskyblue"
        );
        style(middle_panel().compose_box().elem, "background", "cadetblue");

        style(right_sidebar().elem, "background", "darkseagreen");
        style(right_sidebar().shortcuts().elem, "background", "cadetblue");
    }

    setTimeout(tamper, 2000);
})();