How to post to Slack using a third-party script

Or Google Tag Manager, whichever is handier.

Here’s a short snippet of code I used to use to notify my team of recent conversions, as they took place. The delay was less than 3 seconds.

<script>
let url = 'https://hooks.slack.com/services/XXXXXXXXX/YYYYYYYYY/ZZZZZZZZZZZZZZZZZZZZZZ';
let text = 'New event - {{customEventId}} - completed!';

$.ajax({
    data: 'payload=' + JSON.stringify({
        "text": text,
    }),
    dataType: 'json',
    processData: false,
    type: 'POST',
    url: url
});
</script>

Notes & Details

Get the hook URL from Slack.
I initially used jQuery for this, but it can be easily switched to use XHR or Fetch API. It’s pretty old, though, and I won’t do it. I’m not using Slack anymore.
{{customEventId}} is a Google Tag Manager variable.