This DOM manipulation (DOM scripting) can be used in many ways. Via so-called event handlers Functions is initially linked to certain events. These can be Clicks by the user, times or even the loading of the website. Using the ID's assigned to elements in HTML, event-based changes can then be triggered. This can range from programming simple, dynamic forms or table filters to embedding Video-players or complex, dynamic graphics.
Server-side dynamization: AJAX and Node.js