Trying to figure out if passing along an event id through use of a hidden field attached to a contact.

I'm using chatgpt and am not a JS expert so I was wondering if something like this would work to inject the custom field with a value. It hasn't been working for me but not sure if its a code error

<script>

document.addEventListener("DOMContentLoaded", function() {

// Wait until the form is present in the DOM

const waitForForm = setInterval(() => {

const form = document.querySelector("form input[name='fb_event_id']")?.closest("form");

if (!form) return;

clearInterval(waitForForm);

const hiddenField = form.querySelector("input[name='fb_event_id']");

if (!hiddenField) return;

form.addEventListener("submit", function() {

// Generate unique event ID

const fbEventId = "evt_" + Date.now() + "_" + Math.random().toString(36).substring(2, 10);

// Populate hidden field

hiddenField.value = fbEventId;

// Store in localStorage for pixel on next page

localStorage.setItem("fb_event_id", fbEventId);

});

}, 200); // check every 200ms until form is ready

});

</script>

Passing user details as additional fields would be great as well. only if someone cares about their ads. This would be the first step towards imporving pixel installation.

Conversions API Pixel Events. - This would be extremely helpful because it would enable proper deduplication.