A userscript that stops auto-playing GIFs in chat

stopAutoplayingGifs.user.js

// ==UserScript==
// @name         Stop GIFs auto-playing
// @namespace    http://stackexchange.com/users/4337810/
// @version      1.0
// @description  A userscript that stops auto-playing GIFs in chat
// @author       ᔕᖺᘎᕊ (http://stackexchange.com/users/4337810/)
// @match        *://chat.stackoverfow.com/*
// @match        *://chat.meta.stackexchange.com/*
// @match        *://chat.stackexchange.com/*
// @require      https://rawgit.com/krasimir/gifffer/master/build/gifffer.min.js
// @grant        none
// ==/UserScript==

function replaceSrcAttributesAndStartGifffer() {
    //Thanks to Krasimir's gifffer library: https://github.com/krasimir/gifffer, http://stackoverflow.com/a/24314098/ :)
    setTimeout(function() {
        $('img[src*=".gif"]').each(function() {
            src = $(this).attr('src');
            $(this).removeAttr('src').attr('data-gifffer', src);
            $(this).parents('a').click(function(e) {
                e.preventDefault();
            });
        });

        Gifffer();
    }, 1000);
};


var observer = new MutationObserver(function (mutations) { //for NEW messages
    mutations.forEach(function (mutation) {
        var length = mutation.addedNodes.length;
        for (var i = 0; i < length; i++) {
            var $addedNode = $(mutation.addedNodes[i]);
            if (!$addedNode.hasClass('message')) {
                return;
            }

            var $lastanchor = $addedNode.find('img').last();
            if (!$lastanchor) {
                return;
            }
            
            replaceSrcAttributesAndStartGifffer();
        }
    });
});

$(function() {
    replaceSrcAttributesAndStartGifffer(); //for EXISTING messages
	
	observer.observe(document.getElementById('chat'), {
        childList: true,
        subtree: true
    });
});