The following script ensures that my_finalFunction
runs after your page has been fully loaded with images, stylesheets and external content:
<script>
document.addEventListener("load", my_finalFunction, false);
function my_finalFunction(e) {
/* things to do after all has been loaded */
}
</script>
A good explanation is provided by kirupa on running your code at the right time, see https://www.kirupa.com/html5/running_your_code_at_the_right_time.htm.