TIPS
How to make JavaScript execute after page load?
https://stackoverflow.com/questions/807878/how-to-make-javascript-execute-after-page-load
These solutions will work:
As mentioned in comments use defer:
<script src="deferMe.js" defer></script> or <body onload="script();"> or document.onload = function ... or even window.onload = function ...
Note that the last option is a better way to go since it is unobstrusive and is considered more standard.
Example
<script type="text/javascript" src="jquery.js"></script>
<script>
// Check if the page has loaded completely
$(document).ready( function() {
$('#some_id').load('php-file.php');
});
</script>