> If we’re expecting the page DOM to change often (for example, with SPAs), we certainly don’t want to miss out on any valuable data. Just set a MutationObserver to watch the entire page, and reapply listeners as needed.

The code below this text is highly inefficient and may lead the user detection solely from page interactivity slowdown alone. A more efficient implementation could read input using the 'input' event[1]. For example, here[2] is how you would use the input event to detect changes to any fields in a page.

1. https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement...

2. https://gist.github.com/eligrey/615fcc9fa9edbfb5153478109b5b...