In jQuery, if you want an event to work on your page, you should call it inside the $(document).ready() function. Everything inside it will load as soon as the DOM is loaded and before the page contents are loaded.
$(document).ready(function() {
alert(“Document loaded successful!");
});Example
In JavaScript, to achieve the same result like $(document).ready, try the following code −
<html>
<body>
<script>
var loader = setInterval(function () {
if(document.readyState !== "complete") return;
clearInterval(loader);
alert(“Document loaded successful!");
// document.write("Document loaded successful!");
}, 300);
</script>
</body>
</html>