Here’s a quick way not so good way (see update) of getting multiple javascript functions to be called when the page has finished loading.
Add this to the pages Head section:
And then where you need an onload event callback do this:
onload_functions.push(function() {alert('The page loaded...'););
Update:
As pointed out by phihag, this solution isn’t great, instead try using phihag’s code or use jquery and just $(document).ready(function{} {alert('The page loaded...');});.