Javascript script is not modifying the DOM

[Saya47]

Hello I hope you're all doing well!

I'm using --disable-private-mode argument of the Docker image and the default LUA script.

I've made a single page website using Django and the HTML loads a script on head:

<script src="/static/js/modify-the-dom.js"></script>

And all the script does is to write something on the page:

window.onload = function(){
    document.write('Modified the DOM!');
}

This change shows up on the browsers! But on on Splash.

So I was wondering how to fix that. I tried adding bigger wait as well to no avail.
I also checked my Splash with this website and it seems JS is not enabled!
https://www.whatismybrowser.com/detect/is-javascript-enabled
How should I enable it?

I also tried another single page app using React and all it does is add an element to root:

function F(){
  class HelloMessage extends React.Component {
    render() {
      return React.createElement(
        "div",
        null,
        "Hello ",
        this.props.name
      );
    }
  }
  return(React.createElement(HelloMessage, { name: "Taylor" }));
}

But Splash only shows a blank white page!

Thanks a lot!

[GerritGeeraerts]

I also have the same issue where on several sites the java-script is not executing. I also started the docker with --disabled-private-mode

I like your test, that isolates the problem well:

window.onload = function(){
    document.write('Modified the DOM!');
}

There most be something really basic going wrong.
Help would be appreciated!

[Saya47]

@GerritGeeraerts I never figured this out, I moved to using Puppeteer actually. Much better results than libraries currently available on Python.