Append Text in DOM

        <!DOCTYPE html><html><head></head><body>

        <div id="bla">

</div>
<div id="bla2">

</div>
        </body></html>
        
        <script type="text/javascript"> window.addEventListener('load', function() {

        function appendText(element, theString) {
	return element.appendChild(document.createTextNode(theString))
}
function myFunction(number) {
	return number  * 2;
}

appendText(bla, myFunction(1998));
appendText(bla2, myFunction(20) + " " + myFunction(10));
        }) </script>
        
        <style type="text/css">

        </style>
        
        RESULT: (open your console with F12 or CTRL-SHIFT-K)