Facebook mobile on desktop

fb_on_desktop.js

// ==UserScript==
// @name         Facebook Mobile on Desktop
// @namespace    http://tampermonkey.net/
// @version      0.3
// @description  Enhancments for FB mobile on Desktop!
// @author       https://github.com/ugjka/
// @match        https://m.facebook.com/*
// @grant        none
// ==/UserScript==

(function () {
    'use strict';
    var body = document.getElementsByTagName("BODY")[0]
    body.style.width = "500px";
    body.style.margin = "auto";

    document.addEventListener("DOMNodeInserted", function () {
        var stories;
        var composer;
        var extra;
        try {
            stories = document.getElementById("story_bucket_viewer_content").childNodes[0];
        }
        catch { }
        if (stories) {
            stories.style.width = "500px";
            stories.style.margin = "auto";
        };
        try {
            composer = document.getElementById("composer-main-view-id")
        }
        catch { }
        if (composer) {
            composer.style.width = "500px";
            composer.style.margin = "auto";
        };
        try {
            extra = document.getElementById("msite-pages-header-contents").nextSibling
        }
        catch { }
        if (extra) {
            extra.style.width = "500px";
            extra.style.margin = "auto";
        };

    });
})();