Flush tampermonkey changes

Question

I am trying to create a Tampermonkey script to automatically fill a login form with my username and password and then I would like to click the login button. However, with the code below, it appears to wait the three seconds, and THEN it fills the text into the boxes. How can I "flush" the changes so that they appear before the wait time occurs?

Thanks!

(function() {
    'use strict';
     function wait(ms){
           var start = new Date().getTime();
           var end = start;
           while(end < start + ms) {
                end = new Date().getTime();
           }
     }
     window.onbeforeunload = function (){
     return "Leaving page...";
     }
     $(document).ready(function() {
         document.getElementById("username").value = "userValue";
         document.getElementById("password").value = "passwordValue";
         wait(3000);
         document.getElementsByClassName("btn-large").click();
     });
})();

Answer 1

That wait function is locking up the browser tab (and probably the browser, and potentially the whole computer). Don't code like that!

Also:

1. (function() {... is completely superfluous in a Tampermonkey script.
2. $(document).ready(function()... is not helpful except in rare cases that do not apply here.
3. Lots,   lots   more, etc...

Here's that code refactored:

window.onbeforeunload = function () {
    return "Leaving page...";
}
//-- Hacker easter egg!  See linked questions.
document.getElementById ("username").value = "userValue";
document.getElementById ("password").value = "passwordValue";

setTimeout (clickBtnAfterDelay, 3000);

function () {
    //-- Brittle!  See linked questions.
    document.getElementsByClassName ("btn-large")[0].click ();
}