Tamper Monkey script to automatically log into Magento2 admin panel

magento2-auto-login.js

// ==UserScript==
// @name         Local Login - M2
// @namespace    http://your.homepage/
// @version      0.1
// @description  enter something useful
// @author       Sam Tay
// @match        *.dev/*admin*
// ==/UserScript==

// Credentials
var username = 'admin',
    password = 'pass4admin';

// On load, wait for jQuery to come on board, then login
timer();
function timer() {
  if (typeof jQuery === "function") {
    login(jQuery);
  } else {
    setTimeout(timer, 200);
  }
}

// Pass login credentials and submit form
function login($) {
  if ($('body.adminhtml-auth-login').length) {
    try {
      showPopup($);
    } catch(err) {
      console.log(err);
    }
    $('#username').val('admin');
    $('#login').val('pass4admin');
    $('#login-form').submit();
  }
}

// Pop up for tamper monkey, not very important
function showPopup($){
  var docHeight = $(window).width();

  $("body").append("<div id='overlay'></div><div id='login-message'>Logging in with Tampermonkey...</div>");

  $("#overlay")
    .css({
      'height' : docHeight + 'px',
      'opacity' : 0.4,
      'position': 'absolute',
      'top': 0,
      'left': 0,
      'backgroundColor': 'black',
      'width': '100%',
      'zIndex': 5000
    });

  $("#login-message")
    .css({
      'height' : '80px',
      'position': 'absolute',
      'backgroundColor': 'white',
      'width': '200px',
      'zIndex': 5001,
      'padding': '20px',
      'border': '5px solid black'
    });

  var vpWidth = $(window).width();
  var width = $("#login-message").width();

  var avLeft = (vpWidth / 2) - (width / 2) + 'px';

  var vpHeight = $(window).height();
  var height = $("#login-message").height();
  var scrollTop = $(window).scrollTop();
  var avTop = (vpHeight / 2) - (height / 2) + scrollTop + 'px';

  $("#login-message")
    .css({
      'top': avTop,
      'left': avLeft
    });
}

This works great in Magento 2.2.3, thanks Sam!