Web coding languages allow some types of graphics to be created procedurally and used in ways that are not possible with images created with non-procedural methods, in that the images are created dynamically. This means that images can be generated and changed in real time, making them suitable, for example, for generating graphics such as graphs, charts, and maps on the fly, based on, for example, continually changing data supplied by users. The most commonly used Web-specific languages are HTML, SVG, and JavaScript; however, general-purpose languages, such as C++, are also used. The main disadvantage of using coding languages to create images is that programming skill is required and the process can be time-consuming when complex images are involved.
Source: Sklar David (2016), HTML: A Gentle Introduction to the Web’s Most Popular Language, O’Reilly Media; 1st edition.