TamperMonkey - show Twitter User-IDs

showTwitterUserId.user.js

// ==UserScript==
// @name         Twitter UserID
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  show Twitter User-IDs
// @author       You
// @match        https://twitter.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var btn = document.querySelector('.user-actions-follow-button');

    if (btn) {
        var userId = btn.parentNode.dataset.userId;

        var li = btn.parentNode.parentNode.parentNode.previousSibling;
        var newLi = document.createElement('LI');
        li.parentNode.insertBefore(newLi, li);
        newLi.classList = 'ProfileNav-item';
        newLi.innerHTML = '<span class="ProfileNav-stat"><span class="ProfileNav-label">UserId</span><span class="ProfileNav-value">' + userId + '</span></span>';
    }
})();