Improving User Experience with Auto-Focus in 2FA Input

There is a website I log into often that I protect with 2FA. One thing that bothers me about this process is that the 2FA screen does not immediately focus to the input, so I can immediately start entering my 2FA code. Today, I tackled that problem.

The most recent experience I’ve had writing userscripts was with a closed source browser extension. A few minutes of search and I discovered Violentmonkey, an open source option with no tracking software.

My goal was to focus on a an input field (that fortunately had an id) on page load. I created a new userscript with the following content:

// ==UserScript==
// @name        Focus 2FA input - coolwebsite.com
// @namespace   Violentmonkey Scripts
// @match       https://coolwebsite.com/login/
// @grant       none
// @version     1.0
// @author      -
// @description 9/5/2023, 7:51:16 PM
// ==/UserScript==

Next, I wrote some simple Javascript that I tested successfully in the console.

document.getElementById("the-code").focus();

Unfortunately, this didn’t work. After logging document.getElementById("the-code"), I determined the page hadn’t loaded yet to run this code. I tried a few different variants of waiting for the page to load, but eventually got it working with this beauty

(function() {
    'use strict';

    function focusOnLoad() {
        var inputElement = document.getElementById("the-code");
        if (inputElement) {
            inputElement.focus();
        }
    }

    window.addEventListener('load', function() {
        // Delay to ensure the page is fully loaded
        setTimeout(focusOnLoad, 2000);
    });
})();

It’s been a while since I’ve written JavaScript that needs to be supported by the browser natively without a transpiler, so this doesn’t look so fun, but it gets the job done. I had to play with increasing the setTimeout delay, since the target site was doing some kind of bizarre redirect (or maybe was just loading that slowly).