Tampermonkey / Greasemonkey script to automatically set the privacy of replies to unlisted by default on Mastodon.

mastodon_unlist_replies.user.js

// ==UserScript==
// @name         Mastodon Unlisted Replies
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Sets the privacy of replies to unlisted by default on Mastodon.
// @author       Graham Sutherland (@gsuberland@chaos.social)
// @match        https://chaos.social/* https://mastodon.social/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=chaos.social
// @grant        none
// @run-at       document-idle
// ==/UserScript==

// https://stackoverflow.com/a/39165137/978756
function FindReact(dom, traverseUp = 0) {
    const key = Object.keys(dom).find(key=>{
        return key.startsWith("__reactFiber$") // react 17+
            || key.startsWith("__reactInternalInstance$"); // react <17
    });
    const domFiber = dom[key];
    if (domFiber == null) return null;

    // react <16
    if (domFiber._currentElement) {
        let compFiber = domFiber._currentElement._owner;
        for (let i = 0; i < traverseUp; i++) {
            compFiber = compFiber._currentElement._owner;
        }
        return compFiber._instance;
    }

    // react 16+
    const GetCompFiber = fiber=>{
        //return fiber._debugOwner; // this also works, but is __DEV__ only
        let parentFiber = fiber.return;
        while (typeof parentFiber.type == "string") {
            parentFiber = parentFiber.return;
        }
        return parentFiber;
    };
    let compFiber = GetCompFiber(domFiber);
    for (let i = 0; i < traverseUp; i++) {
        compFiber = GetCompFiber(compFiber);
    }
    return compFiber.stateNode;
}

(function() {
    'use strict';

    document.mastodon_unlistreply = {};
    document.mastodon_unlistreply.elements = {};
    document.mastodon_unlistreply.react = {};
    document.mastodon_unlistreply.timers = {};

    // use setInterval to wait for the forms to be set up and working
    document.mastodon_unlistreply.timers.elementFinder = window.setInterval(function() {
        var pagers = document.getElementsByClassName('drawer__pager');
        if (pagers.length == 0)
            return;
        var composers = pagers[0].getElementsByClassName('compose-form');
        if (composers.length == 0)
            return;
        var privacy_dropdowns = composers[0].getElementsByClassName('privacy-dropdown');
        if (privacy_dropdowns.length == 0)
            return;

        document.mastodon_unlistreply.elements.pager = pagers[0];
        document.mastodon_unlistreply.elements.composer = composers[0];
        document.mastodon_unlistreply.elements.privacy = privacy_dropdowns[0];
        document.mastodon_unlistreply.react.composer = FindReact(document.mastodon_unlistreply.elements.composer);
        document.mastodon_unlistreply.react.privacy = FindReact(document.mastodon_unlistreply.elements.privacy);

        // ok, setup complete. kill the elementFinder timer.
        clearInterval(document.mastodon_unlistreply.timers.elementFinder);
        document.mastodon_unlistreply.timers.elementFinder = null;

        // every 500ms we check for changes.
        document.mastodon_unlistreply.timers.update = window.setInterval(function() {
            let composer = document.mastodon_unlistreply.react.composer;
            let privacy = document.mastodon_unlistreply.react.privacy;
            // only care about replies
            if (composer.props.isInReply)
            {
                // get the reply indicator element and component so we can see if it changed since we last touched things
                document.mastodon_unlistreply.elements.reply = document.mastodon_unlistreply.elements.composer.getElementsByClassName('reply-indicator')[0];
                document.mastodon_unlistreply.react.reply = FindReact(document.mastodon_unlistreply.elements.reply);

                // have we touched this composer since it was last updated? (react removes extra properties on update)
                if (!composer.props.hasOwnProperty('__unlistreply_touched'))
                {
                    // there has been an update! mark as touched.
                    composer.props.__unlistreply_touched = new Date();

                    // have we touched the reply since it was last updated? (react removes extra properties on update)
                    let reply = document.mastodon_unlistreply.react.reply;
                    if (!reply.props.hasOwnProperty('__unlistreply_touched'))
                    {
                        // there has been an update! mark as touched.
                        reply.props.__unlistreply_touched = new Date();

                        // if the reply is marked as public and the control is enabled, mark the reply as unlisted.
                        if (privacy.props.value == 'public' && !privacy.props.disabled)
                        {
                            privacy.handleChange('unlisted');
                        }
                    }
                }
            }
        }, 500);

    }, 500);
})();