Tweet icon for Jeeves in SO chat

script.js

// ==UserScript==
// @name         Tweet icon for Jeeves in SO chat
// @namespace    http://room11.org/
// @version      1.0
// @description  @PeeHaa sucks
// @author       @DaveRandom
// @match        *://chat.stackoverflow.com/rooms/*
// @grant        none
// ==/UserScript==

(() => {
    'use strict';

    const imgSrc = 'https://abs.twimg.com/icons/apple-touch-icon-192x192.png';
    const imgStyles = 'width:13px;height:13px;display:inline-block;cursor:pointer';
    const maxLength = 280;
    const command = '!!tweet';

    const input = document.getElementById('input');
    const button = document.getElementById('sayit-button');

    function processMutations(mutations)
    {
        mutations.forEach(processMutation);
    }

    function processMutation(mutation)
    {
        mutation.addedNodes.forEach((node) => {
            if (node.tagName && node.tagName.toLowerCase() === 'li') {
                processAddedStarredMessageNode(node);
            }
        });
    }

    function processAddedStarredMessageNode(starredMessageNode)
    {
        const starContainer = starredMessageNode.firstElementChild;
        const tmp = document.createElement('div');

        let node = starContainer.nextSibling;
        while (!node.href || !node.classList || !node.classList.contains('permalink')) {
            tmp.appendChild(node.cloneNode(true));
            node = node.nextSibling;
        }

        const href = node.href;
        const text = tmp.textContent
            .replace(/^\s+/, '')
            .replace(/\s*-\s*$/, '')
            .replace(/\s+/, ' ');

        if (text.length > maxLength) {
            return;
        }

        const question = 'Are you sure you want to tweet this?\n\n' + text;

        const img = document.createElement('img');
        img.src = imgSrc;
        img.setAttribute('style', imgStyles);
        img.setAttribute('title', 'Tweet this message with ' + command);
        img.addEventListener('click', () => {
            if (!confirm(question)) {
                return;
            }

            input.value = command + ' ' + href;
            button.dispatchEvent(new MouseEvent('click', {view: window, bubbles: true, cancelable: true}));
        });

        starredMessageNode.insertBefore(img, starContainer);
    }

    (new MutationObserver(processMutations)).observe(
        document.getElementById('starred-posts'),
        {childList: true, subtree: true}
    );
})();