Use htmx.onLoad().

Simple example:

<script src='https://unpkg.com/htmx.org@1.9.6'></script>

<p class='mt-5 mb-0' id='last-updated'>Last updated ...</p>
<button
  id='fetch-last-updated'
  hx-post='/partials/last-updated/'
  hx-trigger='click'
  hx-target='#last-updated'
  hx-swap='innerHTML'>
</button>

<script>
  htmx.onLoad(function (el) {
    const contentElement = document.getElementById('fetch-last-updated')
    htmx.trigger(contentElement, 'click', {})
  })
</script>

Lessons in this unit:

0:	Introduction
1:	Why htmx
2:	The core idea of htmx
3:	Installing htmx
4:	Doing a GET request
5:	Swap
6:	POST request
7:	Targets
8:	Loading indicator
9:	Confirming actions, and prompts
10:	Triggers
11:	Request headers
12:	Response headers
13:	Events
14:	Redirect after request
15:	Send files using htmx.ajax()
16:	▶︎ Perform something on page load
17:	Conditionally hide HTML elements based on HTMX request status
18:	htmx + Alpine template tag
19:	htmx, include hidden input fields outside of a form
20:	htmx trigger request via JS event