Filling and Submitting form with Javascript Snippets in Chromium

I am attempting to fill a form and submit on a web page using JavaScript Snippets. Here is the code:

// sleep time expects milliseconds
function sleep (time) {
  return new Promise((resolve) => setTimeout(resolve, time));
}

document.getElementById('username').value = 'user'; 
document.getElementById('password').value = 'password'; 

sleep(1000).then(() => {
    document.getElementsByClassName("loginfloatright")[0].click();
});

The form gets filled out correctly but when submitted I get a form validation error stating that there must be a username and password. I also tried clicking the form fields after I set the value. example: document.getElementById('username').click();