AJO code base experience - element not yet in the DOM

As I read in the documentation code base experiences are run as soon as WEB SDK is loaded. Taking into account that WEB SDK should be in the head section of the page. What if we would like to (as an experience) personalize some banner. Then in the js script we should check if DOMContentLoaded event is fired and the our script should run and then change the banner? What is your experience?