You can create a function to call when the elements are loaded, and another function to check if they are loaded at an interval. Then attach the load checking function to the body's onload
attribute. For example:
<body onload="checkLoaded()">
<script type="text/javascript">
var afterLoaded = function() {
// code to execute once elements are in place
console.log("Elements loaded.");
};
var checkLoaded = function() {
var interval = setInterval(function() {
if(document.getElementsByClassName("hello").length) {
clearInterval(interval);
afterLoaded();
}
}, 1000);
};
</script>