reddit links in so chat

reddit.link.user.js

// ==UserScript==
// @name          Reddit links
// @author        Robert Lemon
// @version       0.42.0
// @namespace     
// @description   replaces /r/something with a reddit link.
// @include       http://chat.stackoverflow.com/rooms/*
// ==/UserScript==
function exec(fn) {
    var script = document.createElement('script');
    script.setAttribute('type', 'application/javascript');
    script.textContent = '(' + fn + ')();';
    document.body.appendChild(script); // run the script
}
exec(function() {
    var re = /(\B\/r\/\w+)/gi;
    function parseNode(node) {
        if (node.classList && node.classList.contains('message') && !node.classList.contains('pending')) {
            if (re.test(node.textContent)) {
                node.innerHTML = node.innerHTML.replace(re, function(match) {
                    return ' <a href="http://reddit.com' + match + '">' + match + '</a>';
                });
            }
        }
    }
    var chat = document.getElementById('chat');
    // get all existing messages
    [].forEach.call(chat.querySelectorAll('.user-container .message'), parseNode);
    // listen for new messages
    new MutationObserver(function(records) {
        records.forEach(function(record) {
            [].forEach.call(record.addedNodes, parseNode);
        });
    }).observe(chat, {
        childList: true,
        subtree: true
    });
});