JavaScript

Please I need help:

changes the background color of the HTML document via using the old DOM practice of setting the document.bgcolor. It works, but it does not use the new DOM API of document.getElementById() nor does it use CSS for styling.
Design and develop an HTML file called: simpleInteractivityWithDOM_CSS.html that will change the background color just as it is done in simpleInteractivity.htm, but via JavaScript setting the background color CSS style rule for the body DOM element.

kind regards
Mustapha